Storage configuration advice - IBM DS3400

[six4rm]

Hi,  I'm after some advice as to how to configure our IBM DS3400 to use within vSphere. The SAN was previously live with around 200 VMs on it, however the people that configured it originally set it up such that there was 1 big RAID10 array which was then carved into 8 datastores. Running in this configuration we ran into all sorts of performance issues relating to disk latency. We've since purchased a new NetApp SAN and migrated all the VMs over to that so the IBM is sitting there doing nothing. What I'd like to achieve is to have a split of VMs across both SANs but I'm not sure of the best way to configure the IBM to get the best performance out of it.  The IBM consists of 12 x 700GB SATA disks. It has dual controllers and connectivity is via FibreChannel. In its previous configuration it was running with a 5 disk RAID0 which was then mirrored with 2 hot spares. I'm thinking of setting it up as follows:  2 x RAID10 each with 4 disks (1.4TB usable) 1 x RAID1 with 2 disks (700MB usable)  My thinking is that with multiple arrays you're not spinning up all 10 disks, as per previous configuration, every time IO occurs. Does that make sense?  Your thoughts would be very much appreciated.

[idle-jam]

RAID10 would actually give the best possible raid configuration for performance. anyway i would stick with RAID10 again but then be careful on the type of VM that are to be put in. afterall it's just sata disks there ..

[AndreTheGiant]

A DS3400 is an entry level entrerprise storage... It does not matter if it has FC connection... on this type of storage the bottleneck usually are the disk.

200 VMs on 12 SATA disks is an high load.

You can try to build 2 different RAID10 group, to give the LUNs of one group to a controller and the other on the second one... Just to use the double read cache and speed.

But scaling of this kind storage is limited.

Andre

[six4rm]

Thank you both for the replies.  So you reckon go for two RAID10 arrays? 1 x 4 disk and 1 x 6 disk with 2 hot spares?  I know the SATA disks pose a performance risk, so I was always going to limit the amount of VMs on the IBM SAN and also use it for ISO storage.

[AndreTheGiant]

Could be also a RAID10 and a RAID5 (depending by your I/O needs).

Make at least two different RAID group is to split the spindles half on a controller and halt to the other.

About SATA disks, I've see that more that  5 VMs for each spindle means usually high latency (of course it depends by your workload type).

Andre

[six4rm]

In relation to the 5 VMs per spindle, in a 4 disk RAID10 array, 1.4TB usable in my configuration, would that be 2 x 5 or 4 x 5 for the array?

[AndreTheGiant]

Spindles = total disks... So 4x5

But is just an average... depends by your workloads type.

And of course by your storage controller cache.

Andre

[six4rm]

Hi Andre,

Thanks for the clarification.

They're only Windows XP desktops and the workload will be pretty minimal. I shall go with a 20/30 split across my two arrays giving 50 VMs in total and monitor latency as I go via ESXTOP.

Thanks for all your help.

David.