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Is there a performance hit with running VM's from ISCSI NAS
Posted: 2. Feb 2012, 16:17
by greavette
Hello,
Does anyone have experience (good or bad) with running their VM's from a NAS device? I'm considering using the following:
Iomega StorCenter 34769 PX6-300d Network Storage - 6x Bays, 2x RJ45 10/100/1000Mbps, 1x USB 3.0, 2x USB 2.0, Support-RAID 1, 10, 5, and 6 (hot spare), all with automatic RAID rebuild and hot swap.
For read/write performance I would use Raid-10 and have a Hot-spare in place.
If you use a NAS to run your VM's, what's your performance like. Is it something you would recommend for our small office production environment?
Thanks.
Re: Is there a performance hit with running VM's from ISCSI
Posted: 2. Feb 2012, 22:32
by Sasquatch
If the NAS has NIC teaming so you can combine the bandwidth of the two NICs as one, then it will certainly help. Having a single link can clog it up pretty fast if a lot of I/O is generated. Remember that the max performance of your machines is limited to your network speed, and the max iops the NAS can provide. So if the Host has only a 10/100 Mbit NIC, it will be unwise to run it from a NAS. A single hard drive runs much faster than the NIC can handle. Same as running 10 VMs with heavy I/O on the NAS when you have only 4 hard drives in it. The iops it can provide is ~190% of a single disk I reckon. You have to look it up though, as it differs from disk to disk what it can provide.
Re: Is there a performance hit with running VM's from ISCSI
Posted: 4. Feb 2012, 16:13
by greavette
Thank you for the reply.
I've been researching ways to run my VM's that are not on the Host. It would seem I have a few options, ISCSI, NFS, CIFS (Samba). It would be easier to buy a NAS with ISCSI and NFS, but I'm concerned about performance. Maybe I should build my own server with Raid and put FreeNAS on it with lots of Ram and 4 to 8 nics bonded in twos.
The requirements we deem important would be performance (we don't want the VM's to run slower than on the host), to be able to migrate or teleport VM's from one host to another in the event a host fails. I don't think I can do that with ISCSI since the host that has the lun can't share it with another host. Teaming our Nics would help with throughput, but I feel we need more than the two offered on a NAS.
Could others on this forum tell me what they have done that has worked well? Did you buy a NAS that gave great performance or did you build your own. We do have a limit on what we can spend so I can't go out and buy a large SAN so I would be willing to put in the time required to build something instead.
Thank you.