How to Choose SSD Storage.
By Lee Johns, Vice President Product Management - Everybody is talking about SSD storage & hybrid storage systems today and there are so many new announcements I can see why it is hard for customers to get under the covers and understand what is best for them. On a simple level there are really three types of Solid State storage platform:
1) Dedicated Solid State. This could use solid state drives or NVRAM. It is targeted towards customers who require high performance at any cost – and it will cost! Examples of the genre are Violin, Solidfire and even HP with its recent announcement of an all SSD HP Lefthand array.
2) Storage systems that can accommodate Solid State as a drive type. These are many. Simply add SSD as you would any other drive type. These are characterized by having lower performance than dedicated solid state plays but have the flexibility of multiple tiers of storage in a single array. Some may even have tiering software to move data from one tier to another. Here you could pick virtually any storage vendor as there are very few systems that will not accommodate SSD storage in some way shape or form. These systems are typically targeting the installed base of customers looking to add solid state to an existing system. Often these systems require sophisticated knowledge of workloads and policy-based management to efficiently leverage the SSD resources. These systems typically do not make the best use of SSD resources as they were not designed from the ground up to do so. However because they are already installed they may offer the right flexibility and cost for your existing application bottlenecks. Customers are prone to costly overbuys as they may have to have their entire volume on solid state to get the performance they need.
3) Hybrid storage systems that use solid state as a cache tier. These systems deploy a new modern architecture that aims to provide the performance benefits of SSD’s while minimizing cost. They typically have sophisticated algorithms that move hot data into the SSD tier on a continuous basis to ensure you get accelerated performance when you need it. Because of this they are able to achieve high-performance with fewer SSDs required and this lowers the cost. These systems also lower the management burden of using solid state as a tier. Examples here vary from traditional vendors like EMC with optional FAST Cache, and NetApp with optional FlexCache, to new startups like Starboard Storage Systems who include the solid state tier as standard in their hybrid storage platforms.
So how do you choose?
First, make sure that the SAN you select can handle your workload environment. If you have unstructured data needs then your choices typically become more restricted as many of the vendors offering SSD do not offer NAS in a single unified platform. Make sure also that it has the software features you need and understand if they are included or expensive add-ons. Want to run VMware. Is VAAI supported? Want disaster recovery. Are application consistent, space efficient snapshots supported and is there built-in replication?
Second, make sure that you have a good sense of the IOPS you require and the $/TB you are willing to pay for your total data sets. All SSD systems do offer very high IOPS (Typically 100K to 1M IOPS) but that comes at a price. The vast majority of customer workloads do not require anything close to this level of performance. A quick calculation from one recent all SSD array product announcement shows a solution cost of @ $74K/usable TB for @ 70K IOPS. YOWZA! Most customers are looking to pay an order of magnitude less. Even if you can afford that, what happens if you also have workloads that require high capacity? You have to buy multiple different systems optimized for each workload and then manage storage sprawl and that is costly in both operating and capital expense.
Third, look at what it takes to administer the SSD resources. How much do you need to know about your workloads? Are you required to configure policy? Do you have predictable or unpredictable workloads? This last question is important because first generation tiering architectures impact performance significantly when they move data and therefore require you to determine when data is moved. This is la less efficient use of your time and requires that your workload needs are predictable.
Finally look at the overall balance you need between $/IOP and $/GB. Do you want to consolidate workloads? What are the varying characteristics of those workloads? What kind of data growth are you experiencing and in what areas?
There are good choices available for all workloads and budgets. If you keep these questions in mind you should be able to zero in on the right SSD enabled storage solution for you.