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Can anybody recommend some good places to get started for learning how SANs operate and the differentiating factors to take into account when shopping for them? I have been tasked with recommending and purchasing a SAN and would appreciate any advice the experts here can give.

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3 Answers 3

up vote 8 down vote accepted

If you like reading Using SANs and NAS is a good introductory book. There are some others that go well beyond that which I will add later.

SNIA has some resources including a Storage Networking & Information Management Primer and they offer training which isn't vendor specific:

FastLane also have a Storage Foundation (SAN) course which appears to be vendor independent.

To get a handle on the different technologies used by the Vendors go to their websites and start researching or contact them and talk to their techs. If you are able to, go and visit their technology centres and see the gear and software in action - I have learnt a lot by just talking to the vendors and taking notes of what they say which is always good for comparing and contrasting the different approaches they take.

If you have got the budget find a trusted third party consultant and engage them as a learning resource and sounding board. We found that really valuable when we started our SAN purchasing especially for interpreting the vendor spin that we had to deal with. If you don't have the budget try and find other companies or organisations in your area that have storage experience and ask them as most people will be willing to share information.

Some things to note and look out for when dealing with storage companies are:

  • Before you start you need to have an idea of which systems and applications you are looking to host on the storage. As Chopper3 has said in his answer do this in the context of performance (throughput and IOPS), availability, capacity and cost. This will put you in a much better position than purely capacity based purchases.
  • Consider how the hosts may be attached as a guide to which networking technology to look at, i.e. FC, NFS, iSCSI, FCOE, DCE etc. This may be guided by the vendor you choose and your own internal networking experience and capability. Though many of the vendors claim they can do all of this you need to understand the tradeoffs and capabilities of each approach.
  • Understand how the software is costed and licensed, is it by capacity, by array, by attached host etc.
  • Understand how they calculate usable capacity and make sure that is the same as your requirements.
  • To avoid sticker shock later on:
    • Ask how much drive, shelf and array and cache upgrades cost - including minimum purchases.
    • Ask how much support and warranty upgrades cost - you might start at standard and want to move to premium later.
  • Try and include as much capability and software you think you need upfront (such as snapshots or replication) as the sticker shock for adding this afterwards can be tremendous. The discounts for this tend to be better on the initial purchase - again sticker shock.
  • If high availability is important ask about the non-disruptive impact of the following. Keep in mind common maintenance tasks as well as unplanned outages. Non-disruptive can mean different things to different vendors:
    • Impact of controller, processor or cache failures.
    • Impact of disk, disk shelf or connector failures.
    • Impact of applying firmware or microcode updates.
    • Impact of adding or removing disks and disk shelves.
    • Impact of adding or removing controllers, processors or cache memory.
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+1 - this is the sort of thing that SNIA exists for –  Matt Simmons Nov 26 '09 at 23:13

You need to decide which two of the following three characteristics are most important to you as you can't have all three;

  1. High Performance
  2. High Availability
  3. Low Cost

Once you've figured out these priorities you'll be far better armed to ask more specific questions. It also might be worth searching on this site for a few keywords as there's been a lot of vaguely similar ones asked previously.

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I like StorageMojo for a lot of discussion about large-scale storage and SANs.

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