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I'm thinking about upgrading the OS / application drive for an HP DL 580 G5 running windows server 2003 64-bit. We currently use 3 75GB 10k rpm SAS drives in RAID 1. The server is mainly used for running a memory and pagefile-hungry application, by about 10-20 people at a time. It has 32GB of ram and 32GB of pagefile, and most of the time the pagefile usage is > 50%. The application in question uses lots of virtual memory even when there is plenty of spare ram available (up to 6GB of ram per session + the same of v. ram, and some users work with multiple sessions). More people are going to be using the server fairly soon, so it's likely that an extra 32GB of ram will be installed to accommodate them.

I have the option of spending ~£2800 per unit to replace the 3 SAS disks with 2 HP SAS SSDs (632502-B21), but I'm not sure whether the expense would be justified by the performance gain in this scenario. Should I splash out on the SSDs, or would it be more sensible to stick with the existing drives?

Obviously this will depend a great deal on how much of a performance gain we get from this particular application (I don't have that information yet), but are there any more general considerations that apply here?

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3 drives in RAID 1? I'm assuming hot spare, but... –  gravyface Mar 3 '12 at 17:32
    
It's a bit of an odd situation - I don't work in IT but this decision seems to have ended up in my hands. I know there's a total capacity of 75GB and 3 drives are used, so it might or might not be a hot spare. Either way, I think we're still probably happy to lose it. –  user3490 Mar 3 '12 at 18:52
    
On Linux MDRaid, you can have any number of mirrors for RAID 1 partitions, I've taken 4 x 1TB drives, and partitioned off a 1GB /boot, then made that RAIDed across all 4, as a mirror. –  Tom O'Connor Mar 3 '12 at 23:25
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3 Answers

up vote 2 down vote accepted

A few things... I'm assuming this is a 64-bit edition of Windows Server 2003 and that your storage setup is a RAID 1 with online spare. Is there any chance Windows 2008 would manage resources better? This seems to be more of an application profiling problem. Are you assuming that using SSDs will help pagefile performance? Do you have any evidence that that's a bottleneck? How are things performing now? Why not try moving the pagefiles to a lower-cost SATA SSD to test the theory before jumping into enterprise SSD drives?

As to your question about the HP-branded SSD drives, the OEM is Sandisk/Pliant. These drives are extremely overpriced at the moment. To be honest, these disks require a deep queue in order to perform well. They fall short in performance in many of my applications. I would recommend a different drive for your application if you're concerned about the cost of the part number you noted. The best performance will come from a STEC-branded SSD, but at an even higher cost. A nice alternative that would run well under a variety of conditions is the Seagate Pulsar SAS SSD offering. The Pulsar.2 in 200GB is a great MLC drive that would come in at half the cost of the HP/Pliant disk.

Other notes... This server has an HP SmartArray P400 controller. It's only a 3G SAS controller. You may want to consider using a 6G-capable controller like the HP SmartArray P410 if you do end up using enterprise SSD drives. Also, do you have a battery-backed RAID cache on the existing controller?

Also, why replace the OS drives? You can add another logical drive comprised of the new disks.

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According to dxdiag it's a DL 580 G5 (I only have remote access to it), but with some customisations. It also has a P800 controller, and more hard drive slots. We would need to replace the OS drives because we already have plans to use all the other SAS slots. I'm expecting to hear back from the application developer fairly soon regarding the potential benefits of SSDs. If they haven't tested it but agree that it might do some good, I can suggest the SATA SSD route. Thanks! –  user3490 Mar 3 '12 at 19:08
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Why not just spend money on more memory rather than SSDs? Avoid swapping altogether...

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I strongly agree. If the computer can take 64Gb of memory, just add the missing 32Gb and disable the swap. Low cost, easy to implement, and much faster than SSD. –  Gregory MOUSSAT Mar 3 '12 at 21:19
    
Thanks, @Gregory. I'll recommend we do that first and then see what happens. –  user3490 Mar 3 '12 at 23:52
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Tbh these high end SSDs do not provide a significant speed increase over midrange enterprise or high end consumer SSDs. What they do provide is higher endurance although given that for each of these you could buy 3 of those, it is not really a cost effective solution for most people. But both a £400 or a £1000 SSD is going to be a big increase in IOPs over 10K or 15K SAS drives.

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