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I know this is a newbie question, but believe me please, I have done extensive research on the web and got some conflicting and old answers (2010-2013). I want to know what people do nowadays (in 2015)

I have a pool of 4 Costco special Dell/HP desktop PC's running Xenserver 6.2 to facilitate our software testing. They all have 24GB RAM, 1 to 2TB 5400-7200RPM internal disks. Our app requires a small MySQL database running on each vm, and we run about 5-8 vm's on each host. We also create/clone and destroy vm's frequently. Initially everything was running fine, but after a while, some vm's seem to be getting so slow to not usable. We bought some 500GB SDD to speed things up, but it can only contains 2-3 vm's with some snapshots. So, I started looking into FreeNAS using NFS. Again it seems to run ok now (not as fast as SSD of course, but usable), but I am worried it might become non-usable again once we start using it. I would like to know:

  1. if NAS is a good option (my research shows conflicting answers)?
  2. How others (budget conscious) setup their Xenserver, maybe I am doing something wrong?

As you can get by now, our budget is tiny, and my boss demanded things to work. Any help is appreciated!! And thanks in advance!

PS: There is plan to upgrade to Xenserver 6.5.

Spock
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  • Spock, are you willing to buy a machine just to run FreeNAS? I've a production XenServer pool with more than 50 VM's running on a single iSCSI FreeNAS storage. – Vinícius Ferrão Jul 22 '15 at 00:07
  • I'm guessing that this question is going to get closed, or at least moved to http://softwarerecs.stackexchange.com/. Most of the StackExchange sites stopped allowing product recommendations (see the FAQs). – Jed Daniels Jul 22 '15 at 00:08
  • Hi Vinicius, one of the developer left the company, so I temporary "borrowed" it to run FreeNAS. It has only one slow 2TB green drive, but 20GB RAM. I am planning to add another mirrored 2TB later this week to see if it will improve performance. But if I can prove this works, I think my boss will let me have it. – Spock Jul 22 '15 at 00:13
  • The problem here is the disks that you have. Using two disks in mirror will not give additional performance. For a VM workload you'll need a huge stripe of mirrors, ZFS is great with caching, but if your data is not "cacheable" it will give you the disk performance. Another thing to keep in mind is that XenServer needs time to coalesce the snapshots that you create. So the storage subsystem must be fast enough to handle all the activity. What you need now is to fill the requirements, like: what's the IOPS needed? Do you really need those snapshots? Can it work another way? – Vinícius Ferrão Jul 22 '15 at 00:16
  • Thanks Vinicius! When you say huge strip of mirrors, how many are you talking about? Also instead of mirroring if I just use a bunch of non-mirrored SDD, will that work? I do like the way the NAS work that you can distribute vm workload easily. I am not sure what our IOPS needs are, but I know we do a bunch of small random r/w from the DB. Also I think you are right about the coalesce, because when xenserver is newly install, all of the vm's were usable, and then some are now so slow that is not usable. – Spock Jul 22 '15 at 22:12

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