Category: SAN

SSD – How much is too much?

Speed, SSD, fast, SAN, NAS
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I wrote an article just a few days ago entitled “Where did the 15k disk drive go?”  It was a short piece, quickly done and meant to draw fairly obvious conclusions.  When given a choice between faster and fastest, for the same or close money, people will always choose fastest.  Little did I suspect the sheer amount of comments and emails that I would get from that article.  It appears that everyone has an opinion on storage technology and how storage vendors build out their appliances.  So, in the spirit of keeping the discussion going, I’ve decided to ask the flip side of most of the comment and email subjects.  “If 15k drives are dead, then how much SSD is too much?”  Let the games begin!

How much SSD?

I heard a Texan once say “How much is too much?  Well, if it’s money in the bank or cows on the ranch, you can never have too much!”  He was talking about things that directly affected his performance as a cattleman and his ability to perform his job or company function.  The same can be said for SSD disk in the ever-changing storage arena of business.  How much is too much SSD in a storage array or on a server?  I’m not talking about the sheer amount of physical space – that depends on the applications and data depositories that the application will require.  Plus a little bit for growth.  What I am talking about is a percentage.  Of 100% of the storage space on a given server or storage appliance, just how what percentage should be SSD – fast but expensive?

In my opinion, much will depend on a storage study.  How many IOPs does your environment need so that storage is not the bottleneck in your environment?  Is there too much latency in your SAN or NAS?  If you don’t know the answers to these questions, then a storage study should be your next step.  Check out my article here.  SSD tends to be the most expensive option in GB/$, but that ratio is coming down as manufacturing processes change and get more efficient.  But we all work in the here-and-now, so as of today, how much SSD is too much in your SAN, NAS, or hyperconverged appliance?

All Flash, or no Flash?

I have seen several examples of SSD ratios, all aided by software in one form or another.  These fall into two camps at either end of the spectrum.

To start, there is the storage appliances with no SSD.  These are fairly simple, and I don’t see them around much. If all you need is an array of large disks spinning merrily along, and your storage goals are met, do you really need SSD?  I have been in proof-of-concept trials where SSD would not make any difference is system performance, until the programmers changed the application code to make it more parallel.

Then there is the “all flash all-the-time” argument.  I am familiar with one storage array vendor that sells an all flash array with compression and de-duplication and claims that across the environment, the cost per used Gigabyte is cheaper than their hybrid array (which does not offer any compression type functionality).  Of course with de-duplication your milage may vary, but that makes a compelling argument for all flash.  There are certain industries where milliseconds matter, like stock market trading, or transaction processing.  Those industries go all flash without a second thought.

The middle ground?

So now we reach the middle ground, where the argument get heated.  Hybrid arrays replace the fastest tier of storage with SSD, or use large amounts of SSD as caches to buffer regular hard drives.  Manufacturers use SSD to take the place of those good ol’ 15K drives, as well as some of the 10k drives, too.  The larger and slower SATA drives remain the workhorses for storage.  Older, slower data goes there to die.  Or at least drive your backup software crazy.

So, where does all this leave us?  Should we go ahead and use all flash since it is the wave of the future?  Since I will be replacing my array as I outgrow it, should I buy affordable now, and look to put in all-flash when it is the standard?  Assuming that I am not a government agency with black-budget trillions to spend, how much SSD is too much SSD?  Looking forward to your comments.

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Where did the 15K disk drive go?

15k disk
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Just a few years ago, everyone wanted disk drives that spun at 15,000 rpm, commonly known as “15k disk”.  Why did people want these?  Well, the faster the spindle turned, the shorter the seek times, the less latency and the faster the writes to that disk.  Since I never worked at any of the drive manufacturers, I can’t really speak to the truth of this, but I do take it on faith.  So when everything on a storage array was spinning disk, why did people want “15k spindles” in the line up?  And since SSD has become so popular, why don’t I really see them anymore?

Why do I want expensive, small disks?

The reason that everyone wanted 15k disk drives was pretty straightforward.  The disk themselves were fairly small in capacity (600GB being a standard size) and expensive on a GB/$ ratio.  But they were FAST.  If there was a target IOPs for a storage array, it was easier to balance out size and speed with a ratio of 15k disk, 10k disk, and standard 7.2k SATA drives.  Speed from the smaller drives and space from the slower drives.  While everything was acceptable ON AVERAGE, the laws of physics still applied to the different speeds of disk. There was a bit of balance that had to happen. You could put your fast access volumes on 15k, but you still needed the SATA drives for the larger storage requirements.  This solution worked, but was expensive – and a bit “hands-on”.

There were even a few manufacturers that started to offer ILM with these systems.  This means that “hot” or active data writes to the 15k disk drives since theoretically the write speed on these is fastest.  Your storage appliance now writes more across the aggregate of your SAN environment.  Once this data is written to the fastest disk on your SAN or NAS, it stays there for a bit.  This logic being that it also has the fastest read times and therefore the best performance when you wanted to recall that data.  These ILM vendors then move the data off of the fastest tier of disk to a slower tier as that data becomes less active or “ages”.  This allowed you to store older, less accessed data on the slower and less expensive tiers of storage.  Because the database has to run quickly, but who cares if it takes accounting a week to get the data for their year-end reporting, right?  Remember that the next time you need that expense report reimbursed!

The next step

Then SSD entered the market.  At an affordable price, that is.  Not only could manufacturers use SSD as caching, but they were large enough that manufacturers could also use them as the fastest tier of data storage in an ILM strategy.  And the form factor of SSD disks allows them to be used in the existing storage appliance enclosures – JUST LIKE spinning disk.  Now, instead of expensive 15k disks, you could put in units in the same form factor that would read and write several hundred times faster than disk.  With the speed and storage capability of SSD, it became unnecessary to use 15K disk in storage appliances for speed.

But I still see some 15k disk out there…

You will still see 15k disk used in local solutions.  A 15K SAS disk RAID 5 array is quite speedy when used in a local physical server.  Virtualization solutions, or database servers will often use 15K spindles for disk targets.  They need sizable storage capacities and quick access.  However, the cost of SSD is coming down.  This allows the justification for installation of SSD disk or arrays in physical servers.  Seagate has stopped development of new models for their 15k disk.  Previously storage technology leapt from Tape to HDD for large data storage like disaster recovery.  Now storage acceptance from high speed disk to SSD will likely accelerate.  Technology to increase access speed, reduce manufacturer costs, and increase storage capacity will accelerate this change.  So long 15k disk, we hardly knew ya!

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Snapshots – Everyday Uses and Hacks

Storage Snapshot
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Creating snapshots in a storage environment is an amazing technology.  The ability to take an instant “picture” of a data volume is a tool that is used in a variety of ways.  It makes your job easier and more manageable.  It can help secure your environment.

Different vendors implement snapshots in various ways, but the general theory remains the same. An almost instantaneous copy of data that may be moved and manipulated by a system administrator.  The theory of this is nice, but how can we USE this functionality.  Can it make their job easier and protect their systems from the everyday issues they see “in the wild”?

With organizations I work with, we see many innovative uses of snapshotting technology.  There are amazing examples of real world IT organizations making their jobs faster, easier, and much less stressful.  In other words, they used “business hacks” to make their snapshots work for them. We will discuss five real world ways to use snapshots that are relevant and guaranteed applicable to your everyday work load.

Snapshots in your DR strategy

The first things that pops into most people’s mind is backups and disaster recovery.  Snapshots produce an exact copy of virtual machines or data volumes that is stored within the storage appliances.  Most vendors allow these snapshots to be replicated or moved to another storage appliance.  This allows you to use an appliance in another location as a disaster recovery site.  Or, it is possible to mount these snapshots as volumes and allow your backup server to incorporate these exact replicas of data into your existing backup or Disaster Recovery plan.

There are several advantages to this approach.  The data in a snapshot is an exact replica in time, so it is easy to manage RPO and RTO.  Also, this approach takes the data backup “offline” of your production servers.  Sure, the network and storage are still involved in transferring this data, but the data transfers happen out-of-band.  This reduces slow systems and lag.  Many vendors now include APIs for cloud storage in their software and storage appliances.  Now, you may back up your snapshots directly to cloud storage.

Update “insurance” snapshots

We’ve all done it.  Installed that patch from our system or software vendor and it breaks the box.  Perhaps breaks is a strong word.  It temporarily overwhelms our system with new features and benefits. While snapshots can’t make the process of ironing out an ornery system update any easier, it can provide you with insurance.

By taking a snapshot before you update a system, you have an exact copy that you know works.  Suppose you cannot straighten out all the goodness that was Big-Name-Accounting-Package 5.0 before Monday 8am rolls around.  Now you have the ability to fail-back to your old system while you continue to straighten out the misbehaving upgrade.  Almost a form of version control for those of you familiar with the software development world.  This nifty trick also works on desktops.  If you are using VDI, make copies of your desktop images and use the same concept.  It may not save you time getting to the next version, but it will certainly save your bacon as far as system up-time and help-desk calls are concerned.

Gold copy snapshots

If you are making snapshots of servers before you upgrade, you are probably already doing this, but we will mention it anyway.  Snapshots are amazing tools for creating new servers, virtual machines, or desktops.

Once you have installed an operating system and all the various patches and utilities that you routinely use – take a snapshot.  Now this new, untouched system as-pure-as-the-driven-snow will be the starting point for all new servers or desktops that you implement.  This is often referred to as the “Gold copy“, a reference to software development and when code is ready to ship out to customers.

This “Gold copy” has standard system configurations already in place, various drive mappings, and config files.  It is all in there.  Sure you may edit some things like network and licensing, but you have a starting place that is pretty solid.  In the future, if you need to make changes then just make changes and save as a new snapshot.  This may not seem like much, but anyone who has built a new system from scratch will tell you that this is a genuine lifesaver.

This concept applies to both virtual machines and stand-alone servers or desktops.  Several customers we work with will use an application to “ghost” images from storage appliances to a new non-virtualized server or desktop.  Mount the snapshot you would like to use as your system image, then transfer it over to your new hardware using the disk image utility of your choice.  Of course, this works best in a virtualized environment, but it is also a valuable tool for the not-yet-virtualized.  By the way, why aren’t you virtualized yet?

Instant data set snapshots

We regularly hear from customers asking how to generate test data for new systems testing.  In several cases, systems administration is tasked with creating data sets that the consultants or systems specialists can use to ensure the systems are working as anticipated.

Instead of this being a problem, use the best test data that there is – an exact copy of your current, live data.  There is no need to create new data sets from your existing data. By creating a snapshot of your current databases, you may test systems with what was once hot and live data.  But, there is no negative impact if this data is corrupted or destroyed.  You can even create multiple copies of this data to use across multiple tests.

Getting around malware with snapshots

Today’s data environment can be a pretty scary place.  Look no further than the headlines to see

Malware, virus, spyware
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stories about malware and ransomware wrecking havoc on organizations.  If the recent exploits of the bad guys is any indication, things are getting much larger in scope.  The WannaCry attack is still fresh in everyone’s minds and is rumored to have effected over 230,000 machines world-wide. It is safe to say that there are external threats to your data that can be remediated with snapshots.

A schedule of snapshots  on your storage appliance is the solution.  Whether this is part of your disaster recovery planning or not, set up a schedule. This concept is similar to the “patch insurance” we discussed above.

By making a number of snapshots over time, we are able to go back to former snapshots and explore these snapshots for malware.   Perhaps we may extract data from our snapshots before the encryption activates.  Of course, data sometimes is lost.  It is up to management to decide to pay faceless hackers for your data or try to recover it via backups and snapshots.

Snapshots have been in the storage technology tool bag for a while.  The technology has matured so that most storage array vendors are offering this functionality.  Over years of working with clients, we have discovered many innovative ways that people are using snapshots.  In this article, I have shared what I have seen, but I am interested in what you are doing with your snapshots.  Feel free to share and let everyone know how they can use snapshots within their storage appliance.

 

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How Do I connect to my Storage Appliance?

Fiber Channel attached Storage Appliance
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In this article, we are examining the third question asked in our original article The Beginners Guide to what to know before you shop for a Storage Appliance.  That question in a nutshell is “How do I intend to connect my storage so that all of my applications can get to it?”  Well, that question begs a good look at your current environment.  Based on what you find, we will determine if you should connect to your existing environment or connect through other dedicated technologies within your existing environment.  There are also other less common methods to connect to your storage.

Using Existing network infrastructure

Is your network stable?  Every network administrator or sysadmin knows who the problem children are in their network.  Do you have any segments or switches in your environment that are currently congested or causing delays now?  Adding storage to it will only exacerbate the problem.  On the flip side of that coin, a well-running network makes adding storage easy and inexpensive.

In addition, the speed of your existing network will come into play.  Depending on your current storage needs, I would recommend that no one attach storage at speeds of less than 1 Gigabit Ethernet. As 10 GigE becomes more affordable and more pervasive in networks, it is never a bad idea to increase bandwidth to your storage.  Fortunately, many manufacturers enable upgrading with field replaceable units.  Speak with the vendor about this ability in the units you are investigating.

Most storage appliances will support a variety of connection protocols.  For storage area networks (SAN), it is important that iSCSI be supported in the unit.  iSCSI will support most of the externally mounted volumes or LUNs (Logical Unit Number).  For Network Attached Storage (NAS), NFS is a popular way of attaching storage for most virtualization shared storage and *nix computing.  These storage protocols may all be supported, or only some of them.  SMB/CIFS should be supported for full functionality in a Microsoft network.

Using Dedicated connection technologies

There are situations where the use of the existing network may not be advisable.  If the network is older or slow, putting the data needs of shared storage on the network will just exacerbate an already slow situation.  In this case, there are dedicated connection technologies that may come to the rescue.

Ethernet connectivity is still a very viable alternative, using dedicated switches and VLANs.  VLANs are Virtual Local Area Networks that allow for the logical partitioning of ports within a switch to create virtual switches and LANs.  This lets you segregate data traffic and dedicate resources to the various ports that may be passing your data traffic.

Fiber Channel (FC) is a mature, well established connection technology.  FC uses glass fibers to connect physical servers to physical storage using light.  While this technology is a bit more expensive than traditional ethernet switches it does have advantages over ethernet.  There is tremendous support for this protocol in software and hardware because it is a very stable protocol developed specifically for storage.  Fiber Channel allows for data to be consistently delivered with very low overhead.  Fiber Channel switches are available to connect servers to storage in a logical mesh setup, but it is also a regular practice to directly connect servers with FC Host Bus Adapters (HBA’s – think of an HBA as a fiber channel version of a network card).  This will cut out the expense of a Fiber Channel switch for smaller deployments.

Exotic Connection methods

In addition to the well established protocols of Fiber Channel and iSCSI, there are other ways to connect storage.  There are storage appliances out there that will allow connection to servers via specialized technologies like InfiniBand, or SAS ports.  There is eSATA that is available.  These various ways to connect range from the super fast (InfiniBand – and expensive by the way) to the fairly common and slow.  “Exotic” connection technologies serve special cases and are outside the scope of this article.  These connection technologies will limit your field of vendors, but not disqualify you from a storage appliance.

Considerations of Connectivity

In addition to the connection methods discussed above, there are also other connectivity possibilities to consider.  Bonded connections is one.  Bonded connections make multiple physical paths (read cables or ports) to appear as one logical path to data.  In essence, two 1GB Ethernet connections becomes one logical 2 GB Ethernet connection.  A single path of bandwidth to the storage appliance will be quickly overwhelmed.  There will be many servers and users trying to connect to the storage.  Bonding allows several ports to simultaneously send out data.  Bonding also helps with failover.

Another consideration of connectivity is failover.  Although it may not happen often, if a cable, NIC, or port fails on the storage appliance or on the connectivity side, all servers using that storage are suddenly unable to access data.  Or all of your virtual machines may come down at once.  You have placed all of your proverbial eggs in that one proverbial basket.  Failover mitigates this risk accordingly.

This is often accomplished through the use of different controllers or “heads”.  Two (or more) controllers allows for multiple disparate paths to the data.  It allows for one head to crash and you still have access to your data.  It allows for one power supply to fail, and you still have access to your data.  Many manufacturers will vary on how they support this functionality, so it is important to research this carefully.  Make sure that the storage appliance will run on one power supply.  Verify that the controller heads support failover.  Implement bonded connections.

Summary

In this article, we have discussed the final question raised in our original article about finding the best storage appliance for your environment.  We have gone over considerations of attaching the shared storage to your existing network, the prospect of attaching the NAS or SAN via new connectivity, or even attaching via a special, non-standard or exotic connectivity mode.  Many vendors support these differing connectivity methods.  Specialized connectivity will limit the number of storage appliances that you have to choose from. Most users know that they are required from the start and can plan accordingly.

 

 

 

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How Will I use my Storage Appliance?

Servers and Applications attached to storage appliance
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We previously discussed doing a storage study for your environment.  This article continues after you’ve done that study and have those numbers to help you in determining what you need in a storage appliance.  In this article we will go into the use scenario for your environment.  In essence, “How will you use this storage appliance?”  What applications will be attached and how many users will be on these applications?  How will that affect what I need in a storage appliance?  This article is designed as a starting point for the novice user, not the storage expert.  It will make you ask the right questions for your environment so that you can find the right answers to get the best solutions for your needs.

So, to determine how we will use this appliance, we need to take stock of our environment.  Don’t worry, this is not as in depth as the storage study.  As a matter of fact, you probably already know most of this information just from administering your environment.  It is just a matter of collecting all of this information in one place and using it to project how you are currently using your environment, and how you plan to use a storage appliance in the future.

Numbers of servers, applications, and users.

Probably the single most important consideration of the storage environment is how many.  This applies to how many servers, applications, and users will be regularly using this storage.  Of course, a storage appliance that regularly supplies data to hundreds of users will have different speed and space requirements than appliances that may be used by only a few users.  The Google and Facebook storage environments will amaze you.  So to start, we need a pretty good estimate of how many physical and/or virtual servers may be attaching to this storage and how many users will be accessing data on it as well.

It stands to reason that a mail server that is supporting a large company will need more storage resources than a server that is supporting a dozen.  More users means more space and more speed.  This should spill over into every aspect of your environment.  The larger applications with more users will need more speed and probably more space.

If all of your applications are inward facing, then your work on this part is almost done.  Many companies, however, also host data or applications for outside users as part of their business model.  Maybe it is as simple as an ordering system that a few trusted customers are allowed access to, or it might be as complicated as you company hosting data as your business model.  Either way, it is important to count outside customers in the numbers that you will use to determine storage requirements.  And those customers may be the most important of any that you have.

Future Growth

Also important, although it is not our primary concern, is future growth.  This includes anything that will grow the amount of storage, like acquisitions.  The current space and number of users will tell us where our storage appliance needs to be NOW.  Several items in the storage study will show us how large we are growing with current users and applications.  Future growth of employees and business units will give us a look into how much larger we may need to grow outside of our regular growth numbers.  Because almost nothing gets smaller, right?

What applications are you using?

The type of application that you plan to run in conjunction with your storage appliance matters, and there are two primary types of access.  The speed of access is important to applications like databases.  The amount of storage is important to applications like file shares and home directories.  Please note that these two types of applications are NOT mutually exclusive.  Traditional applications will use a combination of both.  A pure inventory database is probably running very lean and wants speed.  Especially if it is serving records out to multiple sites or users.  I have never met a DBA that doesn’t want more speed and then even more.  But that database may reference a document imaging system that contains large files.  Or it may have BLOBs inside of it.  These things will increase the amount of space needed, but also require that objects be accessible in a reasonable amount of time.

Do a site survey of the applications and their types in your environment.  It is important to keep in mind that databases are everywhere.  In the traditional applications, but also in your mail application.  In special applications that may be specific in your business.  And CERTAINLY in most business intelligence applications that management may be using.

Is or will virtualization be in this environment?

You may be using virtualization in your environment and are looking to add shared storage.  Or you may be looking to virtualize and want to “do it right” by adding a storage appliance right off the bat.  Neither way is wrong and both can apply to this decision.  A well done storage study includes either the servers that are already virtualized or the servers that you will virtualize.

As a small aside, remember that Aristotle said “Nature abhors a vacuum”.  This is how it applies to you. Only the physically unique servers will not be virtualized once you see how great virtualization is.  I refer to servers with physical hardware that cannot be virtualized.  Like a fax server with special cards, or a huge database server that is clustered for performance or availability.

I mentioned storage space above, and that is an important consideration.  Virtualization makes your physical environment much more efficient.  With additional storage space, there is always the temptation to build more.  More servers, more drives, more home directories with cute downloaded pictures of kittens and recipes.  This is not an “if” question, it will happen.  Since you are virtualized, every manager’s wish list of applications comes true.

VDI

In addition to virtualization of servers, there is always the virtualization of desktops, laptops, and portals. The end users in your business.  VDI is an extension of server virtualization technologies and is making serious inroads into businesses large and small. The advantages make it easy to see why.  While planning actual storage requirements for VDI is outside the scope of this document, it is a consideration.  If you are planning to add VDI into your environment, then now is the time to start planning.  You will need a fair amount of capacity and speed depending on the number of users you plan to support.

If you are not planning to add it right now, then at least consider the ramifications that it could have to your storage environment.  New storage appliances are usually a significant purchase.  Plan on how to expand space and speed capacity on the unit you wish.

Summary

In a previous article, we discussed things that you should look for before deciding on a storage appliance that is applicable for your environment.  In this article, we went over the second of the information gathering exercises – How you intend to use your appliance.  What your current environment entails as far as users and applications, how those applications access data, and the presence of virtualization or VDI in your environment are all important questions to answer.  In the next article, we will look at how best to connect your storage appliance to your existing network.  Do we use existing infrastructure, or will we be adding the newest and fastest tech out there?  Tune in next week!

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The Storage Study – or How do I determine what my environment is using?

Storage Study
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In a previous article, we discussed three important questions to answer about YOUR environment before jumping into a storage appliance.  In this article, we will delve deeper into the first question we asked, “How fast and how much storage do you need?”.  This article is designed for the IT generalist, someone who is looking for some insight on how to do one.

So – how do I tell what I need?  The first step is to do a storage study.  The storage study is done in your environment for a period of around seven days.  Why seven days?  Because that will capture an entire work week of your environment.  And by work week, I mean those weekends that systems guys work and backups run on as well.  Is Saturday a full-backup day?  You want to see what the impact is on your systems.  Perhaps accounting prepares reports for payroll on Wednesdays.  Usually, a seven day sampling of your storage needs will account for standard practices within your environment, and not create information stores that are massive in size.

If you would like to capture more days than seven, break it out into multiple capture files of seven days.  Perhaps doing multiple sampling weeks during significant system events would reveal more details about your environment.  End of the quarter accounting processing?  Start of a new production cycle?  You decide.

The storage study should include several important take-aways collated and also broken out by host or server.  These four important metrics are IOP/s, Latency, Storage Footprint, and information on new (or “hot”) data.  We will delve a bit deeper into what each of these means below.

Input/output OPerations per Second (IOP/s)

What is an IOP, and what does it mean to my environment?  IOP/s simply put are a measurement of how many storage operations your host is doing every second.  IOP/s can be misleading, though.  While a single read operation generally takes 1 IOP, writes to disk can use up to 6 IOP/s for the same bit of information.  Why this happens is a bit technical, so your relevant question should be “How do I account for this?”

In addition to the overall IOP/s number, most studies will include a read vs. write percentage. This is usually written as 65/35, or 65% reads across this study and 35% writes.  This percentage determines how exactly to account for the IOP/s that were collected.  Of primary importance to the IOP/s study, though is the IOP/s over time.  This will help determine when the busy parts of the day are.  You should see numbers for absolute peak (meaning that this was the largest IOP/s event during the entire sampling period), and several percentiles.

The 85th percentile number is what is usually used to determine how to size your system.  You can certainly size your system to accommodate your peak IOP/s, but usually this is more appliance than you really need.  It follows the same logic of building a house that is above a 500 year flood plain.  Sure, your house won’t get flooded out (statistically speaking) for 500 years, but will the house even be standing by then?

Latency

OK – we know about how many IOP/s our systems are using in the course of our storage study.  Now, how long is it taking those IOP/s to be serviced?  In essence, your systems are issuing commands to your storage, but how long does it take your storage to complete the command?  Is that number acceptable?  Milliseconds are the usual time.  Lower is better.

Peak and trending latency are important.  If peak latency reaches 100ms, there is cause to investigate further.  Most applications are tolerant of high latency.  High latency is noticed in database record access times, or the spinning wheel/hourglass of uncommitted data.  It can be a bit tricky to run down exactly where the slowdown may be occurring.  Our primary concern with this storage study is that it is NOT happening along the disk I/O path.  Common culprits are slower disks, inadequate system RAM, and older CPUs.

If you start to see this number trending up or if you see spikes during the day, this is indicative of concerns in your system. While your disk storage may not be the bottleneck, we would like to be able to disqualify it.  Your planned storage appliance should be sized to accommodate any extra load.

Overall Storage footprint

Overall footprint is straightforward.  How much stuff do you have stored on all of your systems?  You will see this represented both by the server and also the entire environment that you collected.  This is often represented by a total amount of space in the environment – all the space on all the hard drives.  The amount of used v. free space is important.  This lets you know how much of all the spinning disks that you are have filled with your data.  A small amount of data on a fast, expensive disk or disks is not cost effective.

If you conduct multiple storage studies, compare the amount of used space from one study to another. This will give you an idea of how quickly your environment is growing.  Most of the storage study tools out there will collect information on each disk individually.  This allows you to drill down to the application level.  Find those greedy disk hogging applications quickly.

This metric will help you to determine how much overall space you should put into your storage appliance.

“Hot Data”

Hot data is data that is accessed, changed, or newly written by your systems within the storage study collection period.  In essence, this is the data that your applications used during the study.  All other data is not accessed, touched, or read during this time, but may be necessary to keep.  This hot data contains clues into how much your overall data needs may be growing every week.

Hot Data also answers the question of how fast your storage needs to be.  Writing data puts more of a strain on a system than reading data.  Hence, we need a faster system the more writing we do.  Hot data also gives us a rough estimate of what new data was written on the system.  This allows us to extrapolate what your storage needs will look like in a quarter or a year given your current rate of growth.

One important aspect that hot data drives is the speed of the storage appliance.  The higher the percentage of hot data the faster the storage appliance needs to be.  The larger the overall amount of hot data, the faster the storage appliance needs to be.  These are important considerations in correctly sizing storage appliances for both size and speed.

Accurate growth rates allow us to properly size the overall storage capacity of a storage appliance.  No one wants to buy too little space right off the bat.  But it is also pertinent that we not buy too much storage at the onset of the project.  Storage prices go down every year as capacity goes up.  It is financially cheaper to only buy the storage when you need it, not buy it all up front.

Summary

A storage study is the first step in determining your needs in a storage appliance.  This report generates many of the metrics that are required to correctly size a storage appliance.  The numbers generated will give us ideas of how much disk space overall we need, and how fast that disk space needs to be.

We have discussed IOP/s, Latency, Storage Footprint, and information on new (or “hot”) data in this article.  Once you have collected these metrics, analyze them.  Next, let’s see how various applications affect our storage needs.

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The Beginners Guide to what to know before you shop for a Storage Appliance.

Checklist for storage appliance
Answer these questions to determine your best fit storage appliance.

This is a basic guide, meant for the jack-of-all-trades, not the storage professional. There is a dizzying array of storage appliances on the market.  Appliances with a list of features that would make a Swiss-Army knife blush. We could argue the pros and cons of specific features all day, but this article is more focused on the IT generalist.  More to the thinking, “Will this storage appliance help my business?” As such, we will discuss three initial questions to answer before starting the process of determining the best storage appliance for your environment.

These three questions are 1) How fast and how much storage do I need, 2) For what purpose do I need this storage, and 3) What technology will I use to attach this storage to my environment?

How much, how fast?

So – How much Storage Appliance do you need, and how fast does it need to be? In simple terms, it is time to do your homework. You can collect data on your network using a multitude of tools.  The common term for this work is a storage study or survey. In this study, you or an IT engineer will usually activate utilities that are already on your various systems.  These utilities collect information about how you use your storage on your various boxes over a period of time. As far as the sampling period goes, the longer the better with about 7 days being a happy medium.

Depending on how many systems you have at your location, the collation of this data can be a bit of a beast.  There are several vendors that have tools to help collate this data, and they are both free to download and worth the effort.  Here is a sample report of a personal favorite that supports individual systems as well as VMWare. Click Here to download a copy to run in your environment.

This collection of data will give you insight into how much data storage your environment uses, how often that data changes, and how fast your systems are trying to write data to that storage. This is fairly equivalent to horsepower and gas mileage in a car. There are several subtle nuances that will become important later in the decision process, but this collection will get you the information to start.  It is possible to put together a good picture of your environment, once you get this information.  Data show where you are and allows some assumptions as to how you may use data in the future. You will run into terms like Input/Output Operations a second (IOP/s), latency, and queued operations. Save the questions for later, we have more work to do.

How will I use my storage appliance?

How you intend to use this storage is an important factor in what storage is best for you. Is this storage for a single application like a database, or do you plan to share this storage across several servers and allow them to each use a portion of it? This may determine the sort of connectivity that you need. In addition to the number of applications that may be using this storage, what are those application doing? Databases tend to need more structured access to data and the faster the storage is, generally the better the database will perform. If you have several people on the database at the same time, this may become a factor. Also, for general storage, speed isn’t always the issue as much as perhaps usable space.

Is virtualization a factor in your storage decision? To achieve a truly virtualized environment, there must be shared storage between physically separate hardware servers. If you are virtualized, or plan to, this can be a factor in the type of storage that you choose. If you have considered VDI (virtual desktop infrastructure – or the “virtualization” of the desktops in your environment), then that will most definitely be a consideration in your decision.

How do I attach?

How do you plan to connect your storage to the hungry applications that need it? Unlike traditional direct attached storage, a SAN or NAS doesn’t just clip into your server using existing slots in the chassis. There is a bit of planning involved.

The most common ways to connect NAS and SAN devices is using your existing network. No problem if your network is serving your needs well.  If not – then there is some planning needed into how to best get your applications connected to the data that they crave. Fortunately, the numbers that we collected in the storage study will give you some insight into this. There are alternate ways to connect the storage, if your network isn’t cutting the mustard. Some are best for databases, some are designed to allow low-cost access and growth, and some are hugely expensive but fast as blazes – definitely used for specialized applications. Just collect your thoughts on this and we can use it in a further discussion.

Once you have this information collected, you are well on your way to the having the information that you need. Having done a storage study, determining how you intend to use your SAN, and determining how you will connect servers to the storage will start you in your journey to find the correct the SAN or NAS for you.

We will address each of these questions in more depth in future articles, so stay tuned.

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