On Mar 21, 2011, at 3:21 PM, Emmanuel Noobadmin <centos.admin@xxxxxxxxx> wrote:
>> Since your exporting the storage as iSCSI, the host machine will see
>> it as a raw disk, irrespective of how it's setup on the exported
>> server. So, yes, you can do this.
>
> Sorry for my ambiguity, I meant that mdadm would be on the host machine.
>
> e.g. Using just a 2 node, raid 1 situation
> Storage 1
> -> Disk exported on 192.168.1.10, 192.168.2.10
>
> Storage 2
> -> Disk exported on 192.168.1.20, 192.168.2.20
>
> Host
> -> mdadm multipath md0 = 192.168.1.10, 192.168.2.10
> -> mdadm multipath md1 = 192.168.1.20, 192.168.2.20
> ---> mdadm raid 1 md2 using md0 md1
Yes this will work, dm-multipath and mdraid use different subsystems.
Configure open-iscsi to log into the two targets with two sessions each, setup the dm-multipath to arrange the sessions as either a round-robin or fail-over, then create a mdraid RAID1 out of the two multipath targets (use their multipath identities not their raw identities).
There may be timing issues on system shutdown/startup, so test that fully and tweak it until it starts up properly without requiring a resync.
-Ross
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