I have an EqualLogic iSCSI SAN with SAS drives in RAID-50 with two hot spairs and it runs great. With the two hot spairs, I'll have a drive repalcement for the one that fails within 4 hours from Dell so I'm not much worried about it.
I use Gbit Cisco Catalyst switches. Since the EQL SAN has redundant modules, one module on one switch and the other on a seperate switch. Each switch trunked by multimode fiber.
On your virtual host servers, traffic dedicated for the iSCSI SAN should be seperated from regular network traffic to the virtual instances.
I tend to stay with 2 TB max per volume. Mostly because I work with VMware and that is the max recommended size of a VMFS store.
If you have big capacity drives - go with RAID60. Recovery times will be so big (otherwise performance will be too much degraded) that one more failure and you will loose the data. 24TB storage - took more than week to recover disk. You don't want anything to happen to your data during that week. Since 2003 all what we got is RAID60 (but we didn't switch to TP - I think RAID60 is enough)
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Now my question for a iSCSI environment for Virtual Machines which would be the most ideal performance and reliability wide.
If performance is important to you, I would highly recommend that you use RAID10. With RAID5/50/6/60, your read performance is going to fall through the floor when the array is in a degraded state. In normal operation, you also have to deal with lower write performance due to partial-stripe writes.
Originally Posted by Steven
Stay away from the ZFS Ask Scott from bqinternet about his zfs experiences
In theory, ZFS should be great, but plenty of people have had a lot of trouble with stability and performance. You'll hear a lot of reports that "it's getting better", which it is, but I have no intention of even looking at ZFS again for what we do until there's a consensus that the problems have been fixed.
For simple ZVOLs as iSCSI targets, ZFS might be fine. The code path for a ZVOL is a lot shorter, and there's much less than can go wrong.
Last edited by bqinternet; 09-20-2009 at 12:12 AM.