Monday, September 13, 2010

Buying A Storage Array? 5 Questions You Should Ask!

Buying a storage array can often feel like buying a mattress. The product is the same but the labels are different so you're not certain you are comparing the same thing in the same way. There are areas in life you can scrimp on, but SAN storage and mattresses aren't among those. The choice you make will impact your daily life for years to come so buy the best you can afford or suffer the consequences. To help with that there are at least 5 questions, in no particular order, you should ask of each storage vendor you interview:

1. How far does the array scale and what happens after that? Any array that shares a back-plane, or has in-band controllers is limited in its ability to scale. Some will grow further than others but all have limits. Will you outgrow your array during its 3-5 year lifetime? If so, what happens when it is maxed out? If it means you will have to purchase another system have you factored that into the total cost of the solution? Too, when a vendor tells you how large a system will scale, do they have actual instances of this configuration in the field. More importantly, do they actually have a fully scaled system running in their test labs? It is surprising how many storage vendors publish maximum configurations for their arrays but have, in fact, never physically tested the configuration. If your vendor of choice has never physically tested their maximum configuration you have no reliable assurance it will scale as promised. Weird things happen on large scale implementations.

2. Is it future-proof? Storage arrays are subject to all the same obsolescence issues as any other computer technology. The problem is storage arrays are more expensive than your typical server so there is more at stake. Does the architecture of your chosen system lend itself to future-proofing? It's probably safe to say that no technology is completely future proof but there are architectures that are far closer than others. A storage array with a tightly coupled architecture such as a back-plane do not lend themselves to future-proofing in that their hardware is at the mercy of the oldest technological component. Modular systems that are only dependent upon their connectivity path are the most future-proof since connectivity (Ethernet, Fibre Channel, etc) change far less radically than hardware components such as bus speeds, processors, etc., and since modular architectures are loosely coupled you don't have to change out everything to take advantage of newer technologies, usually you can simply plug them into the architecture next to the legacy equipment. Oh yeah, one other thing in this regard, is there some hidden reason why you are getting such a screaming deal on the storage array under review? Could it be that the array is officially (or more likely unofficially) end of life? When is the next hardware refresh coming out? What is the upgrade path and price? Are you being sold old technology?

3. What does the system cost in total, including all licensing and maintenance fees for the 3-5 years of its life expectancy? Have you ever price-compared systems and found one vendor was substantially less expensive than the others? Or, perhaps one vendor was substantially more expensive than the others. Why the discrepancy? There can be several reasons. When a vendor is substantially less expensive than its competitors there is usually something missing from the configuration. The missing piece is often tied up in licensing fees and version charges that will be needed in the future but not at the time of purchase. This makes the system appear less expensive but in actuality it is a smoke-screen. Storage vendors, like the rest of us, have found it is easier to ask for forgiveness than permission and so they leave these items out to win the deal and hit you up for them later when you are stuck. The cure for this? Get total cost of ownership in writing for the expected life of the system. Have it include any and all future software licensing fees, all capacity fees, all maintenance fees. Stipulate that any omissions are the sole responsibility of the vendor to care for. Will the next hardware refresh require fork-lifting out your array? What is the cost to upgrade? Who does the work, you or the storage vendor/integrator? Does your quote include these cost projections? Can you opt out of the upgrade? Will the storage vendor sock it to you on maintenance in order to get you to upgrade or will your maintenance costs remain the same?

4. Of the raw capacity you purchase, how much data can you actually store and stay within vendor best practices? Capacity is a tricky area with storage arrays. Hard drive vendors calculate storage using the decimal system, operating systems calculate capacity using a binary method. The resulting difference is about 9% meaning that a 1TB hard drive will actually store about 9% less than 1TB (931.32GB); subtract another 20% for a typical RAID 5, 50% for RAID 1. Adding to the capacity pressure is feature, performance, and hot-spare requirements which further limit the usable capacity. To avoid the tricks played in this area, customers should absolutely insist on storage vendors supplying enough capacity to store the actual data the customer intends; after RAID; after feature hold backs; after hot-sparing; and with the level of performance expected despite the capacity being full (best practices “full” not necessarily physically full. Most vendors cannot perform adequately beyond 75%-80% of capacity after RAID and they will have a "best practice" target you should abide by). Stipulate to the storage vendor that they are responsible for supplying any additional hardware at no charge should the system not perform as promised and expected for its intended design and workload. You will find your quotes will become much more realistic and accurate minimizing the risk of your falling victim to a storage vendor's competitive pricing games.

5. What are the "Gotchas" that can come back to haunt me? Usually this falls into the category of "questions you should have asked but didn't know you needed to." Storage vendors know the most common mistakes made by customers that leave them upset and scrambling to rectify. Tell your vendor-of-choice you want to avoid this even if it means paying more up-front and ask them for guidance in avoiding the "gotchas." Storage vendors who speak often of forming a partnership, a trusted adviser relationship, should be willing to honestly help you avoid the pitfalls of not knowing what you don't know. They should tell you about the extra cost incurred with different rev's of software, the licensing costs beyond what you initially purchase. If you are getting a "sweet deal" from a storage vendor you should be aware of how that storage vendor intends on "getting well" financially in the future. Nobody gets something for nothing, not even you. Sales teams who are allowed to give you a "sweet deal" by their management have to have some plan for making up lost revenue. Find out how they are going to do it and make sure you are okay with the plan.