I'm building a iscsi storage system for hosting about ~500 Vmware vm running concurrently. And I have a disk array with 15 disks, I only need moderate write performance but at least raid1. so, that leaves me with RAID1 / RAID10 , I have couple choices:
1) 3x LUN 4disk RAID10 + 3 hot-swap
2) 1x LUN 14disk RAID10 + 1 hot-swap
3) 7x LUN 2disk RAID1 + 1 host-swap
Which way is better? Is there a real problem running 500 vms on single LUN? and would it be better to resort to 7 LUNs so each VM is better isolated with each other?
To save you some mocking, right now I have a LUN with 300 vms running on it, and they are doing 3000-4000 IOPS on this 14disk radi10(in aggregate), and I think that's not too bad. And I want to know if anyone is doing similar things.
I think multiple datastore on single disk array will not work well because I also want SIOC to balance the IO from different VM and I don't think it will work well with some input not under its control.
More Edit: 250k for 500 vm, so you are targeting at 500$ per VM, I can just say wow. It would be cheaper for me to simply buy a single machines with 2 disk for each VM and that would still fit under that budget (they will use more power though). Like I said, I am only looking for moderate performance , it's not like I want to host 500 database vm and expect them to all run at full speed
I ends up using about 200VMs per LUN , each VM has 2 disk , so 400 virtual disk per LUN (14D raid10) and that's working perfectly fine. a little tweak here and there, if you can afford a UPS you can use WB cache to further sky rock your performance.
And at this level, nothing is sequential, all random access, so queue depth is never a issue anyway.