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Re: [Xen-users] Zen backup and failover

On 13/03/13 00:05, Sean Greenslade wrote:
> On Mon, Mar 11, 2013 at 11:25 AM, jacek burghardt
> <jaceksburghardt@xxxxxxxxx> wrote:
>> What is the best open sourced free tool that will synchronize local lvms to
>> iscsi and allow fail over to iscsi targets.
> I (personally) have never seen such a tool, free or commercial. I
> don't know if it's even possible to have a failover block device
> (devs, feel free to shed some more educated light on this). In most
> cases, having block devices fail is rather rare, and is not an event
> that most systems can recover from gracefully. Failover systems
> usually involve hot-spare servers, where the file systems are either
> common or synced in some manner.
> I suppose you _could_ set up a mirrored LVM volume with your local
> disk and your iSCSI target as PVs, but I don't think I would recommend
> that. Instead, I would take a second look at your architecture. If you
> have an iSCSI system in place, it would be better to build RAID / LVM
> mirroring into the iSCSI unit. Let your storage system deal with
> storage availability.
One method to do what I think you are asking is:
You have two storage servers and one or more xen hosts.
Each storage server will have a local block device of the same size as
the other (could be hardware raid, md raid, or plain disks)
Use DRBD to keep the two block devices in sync (similar to RAID1 between
different boxes), use dual primary mode.
Use LVM to divide up the space on the block device as required.
Use ietd (iscsi) to export the LV's

On one or more xen hosts, use iscsi-target to connect to the LV's, each
LV will be presented as a block device /dev/sdX
Now use multipath to connect to both hosts, but use failover mode such
that you won't use the second target unless the primary fails.

I think this should provide a pretty good solution....

Would be nice to hear if you do this and how it works out......


Adam Goryachev
Website Managers

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