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I am looking at building a server for a friends business. This would probably be a SuperMicro job to come in on a small budget, 9 series with Sandy Bridge Dual Socket 2011 26xx processors.

I'm looking to maximize price/performance. Who isn't? Right? Well, I've been looking at the cost of 15k SAS 6Gb drives vs SSD's, and the price is fairly comparable. The advantage being that I wouldn't need a SAS controller and could get by with a good SATA 6Gb controller (half the cost). Also, SSD's give off considerably less heat.

However, I realized that I'm not sure what the disk usage profile of exchange and MS CRM (which are the two major apps that will be running on the server). How much do either Exchange or CRM (ie sql server) write and rewrite to the disk for light usage scenarios?

My concern is that either Exchange or the CRM's SQL Server will make excessive writes, and wear down the SSD's in an overly fast timeframe.

Is anyone aware of the Exchange and Sql write characteristics? Will using SATA 6Gb/s SSD's with 95,000 IOPS compare favorably to similar 15k SAS? SAS of course has advantages of SATA, but would SATA SSD's cancel out those benefits?

Arun Vinoth-Precog Tech - MVP
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Erik Funkenbusch
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I'd stick with a real SAS RAID controller since they can also address SATA drives (including SATA SSD's).

My experience with Exchange 2010 is that it seems to try to do everything to minimize disk I/O. RAM tends to be more important because of caching and what seem to be coalesced writes. I'm only using Exchange in 150-user and less scenarios, though. I'm not sure on the CRM side... Possibly a 50/50 mix of small random and sequential I/O.

Small budget doesn't necessarily mean you need to compromise. Buying a SATA-only controller is a bad compromise. The value in SSD's here would be that you'd need fewer of them to achieve the I/O that a larger number of rotating hard disks could achieve. That's assuming you've figured out what your storage capacity needs are. Please RAID the SSD's (4 or more drives) and don't worry about wearing them out at this point...

ewwhite
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  • Valid point about the SAS RAID controller. My thinking though is with the much higher IOPs in an SSD that cacheing on the RAID was less important, so I could get by with a cheaper controller. Yes, I was planning to RAID the SSD's. I'm basically thinking 3 256GB SSD's in a RAID 5, vs 3 300GB 15k SAS drives in RAID 5. Does the SAS command set and dual porting give SAS an edge over the SSD's or does the higher thruput of the SSD's cancel out the SAS advantage over SATA? Endurance wise, I don't want to have to replace the SSD's in 6 months or a year. – Erik Funkenbusch Nov 01 '12 at 07:49
  • What's your budget? – ewwhite Nov 01 '12 at 08:00
  • I'm hoping to spend less than $1000 on the storage subsystem (controller + drives), and need 5-600GB of storage with redundancy and striping. Not sure if Raid 10 would be any advantage with SSD's over Raid 5 – Erik Funkenbusch Nov 01 '12 at 08:09
  • @MystereMan Total budget. I buy HP servers, for instance. I never have to buy separate RAID controllers. – ewwhite Nov 01 '12 at 08:12
  • around $3k, which is why i'm thinking build vs buy, since I can shave some of the cost there. – Erik Funkenbusch Nov 01 '12 at 08:19
  • I'd seriously just buy a Westmere-based HP off of eBay or through the refurb channels. ML350 G6 tower or DL3xx rackmount. You'd get disks and write cache as well... But, to answer your questions, RAID5 is okay with SSD. RAID 1+0 is better. Battery-backed cache is good on the controller. I'd do 4 disks. At the low-end, Sandforce-based SSD's are good. Dual porting and 3G versus 6G won't make a difference. Avoid RAID 5 with rotating hard drives. – ewwhite Nov 01 '12 at 08:24
  • Not interested in a Westmere. Sandy Bridge is a lot better performance for the price. More cores, more cache, higher QPI throughput, 2-3x the numeric processing power, less power (thus less heat), better virtualization support.. there's no comparison (i'll be running Hyper-V on this with 2-3 VM's) – Erik Funkenbusch Nov 01 '12 at 08:39
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    Exchange 2010 is optimized for low IOPS, by caching a lot of stuff to RAM and read/write sequentially when it can. In other words, it works just great on regular 7200RPM's in RAID5 (careful!) or RAID6. – pauska Nov 01 '12 at 13:04