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Our lead tech wants a SAN.

We have 2 -2950's and 2- 1950's. all dual quad core, 73gb 15K drives, 16gb each. 8 drives on DB each and 4 drives on WS each.

our application is based on .net 2.0 running on iis 6.

I understand having a san will help with a quick restore in terms of DR, but will it actually increase the speed of our app?

what will give us the fastest bang for the buck if not a san?

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closed as not a real question by EEAA, Tim Brigham, John Gardeniers, Ward, Shane Madden Feb 11 '12 at 8:00

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

    
The real question is: do you have the skill set to manage a SAN? Virtualized storage is great for many reasons, but the learning curve for these and other associated technologies is fairly steep. –  EEAA Feb 11 '12 at 4:45
    
i do not currenlty, but i read a dell md3000 is not that hard to manage once set up properly. 15 x 146gb is what had been proposed. –  Alex Feb 11 '12 at 6:27

2 Answers 2

up vote 5 down vote accepted

Hard drive speed and quantity is only a small piece of the disk performance picture. You also need to look at your workload characteristics, caching configuration, disk alignment, RAID array type (1+0 vs. 5/6), segment size/stripe width, and whether you're inadvertently mixing random/sequential workloads (or multiple sequential workloads) on the same set of spindles in such a way that it drags your application performance. If you can't get these basics down on local disk, a SAN is unlikely to help you besides providing you with the ability to add more spindles (disks) to service your I/O requests.

A SAN represents a significant initial cash outlay, a significant yearly support/maintenance fee, a significant amount of supporting infrastructure (iSCSI/Fibre Channel), and a significant amount of learning to support correctly. Unless you're really sure you need one, you should probably exhaust all the other ways of improving your application's performance first.

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so you are saying perform a audit with all the above metrics first to determine if a san would help? we run raid 5 now, but looking to move to raid 10 in the future. –  Alex Feb 11 '12 at 6:28
    
RAID-5 is probably not a bad fit for read-heavy workloads like on most web servers (unless you're prone to failing disks; degraded arrays don't perform well). However, RAID-5 is atrocious at writes unless your application is really predictable and you really know what you're doing tuning it. RAID-10 is much better-performing all around and your database in particular should see much better handling of operations like index updates. –  jgoldschrafe Feb 11 '12 at 13:48

A SAN can provide performance increase but is not a magic cure all. You need to look at some detailed performance metrics to determine the reason for the slow behavior. Check out perfmon and go from there.

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