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Re: [Xen-users] How to make network storage high available?

To: "Matthew Wild" <M.Wild@xxxxxxxx>
Subject: Re: [Xen-users] How to make network storage high available?
From: "Angel Lopez" <angel@xxxxxxxxxx>
Date: Tue, 27 Mar 2007 22:51:42 +0200 (CEST)
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>> It is not needed. A shared iSCSI disk (with the same name in both dom0s)
>> is okay.
>>
> This is how we have set things up. Nominally I have two storage servers
> connected with drbd, sharing lvm2 volumes through iscsitarget and multiple
> xen dom0 boxes. Each dom0 box connects to the storage box using iSCSI with
> consistent naming of the devices from udev.
>
> Then run reiserfs, swap, etc on these partitioned devices, and live
> migration
> works a treat. No need for anything cluster aware so far.

Think about a live migration of a VM that is writing to the disk, could it
be possible, during the live migration process, that the VM being migrated
runs in both Dom0 at the same time? If it happens the same DomU will be
writing to the same iSCSI target and no cluster filesystem is in use.

It's OK if the DomU doesn't run in both nodes at the same time, but I'm
not sure about this point in a live migration procedure. I am worried
about this because I did some testing with this and when I performed live
migration of a VM that wasn't writing to disk, it worked fine, but whith a
ftp filw downlad it hangs. The VM root disk was a file exported as a iSCSI
target not a LVM logical volume, maybe this was the problem?



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