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Re: [Xen-users] Xen-DRBD Migration question

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Subject: Re: [Xen-users] Xen-DRBD Migration question
From: Bart Coninckx <bart.coninckx@xxxxxxxxxx>
Date: Fri, 13 Aug 2010 10:05:18 +0200
Cc: Valerio Granato <contact@xxxxxxxxxx>
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On Friday 13 August 2010 02:12:10 Valerio Granato wrote:
> ---- Original Message ----
> From: "Bart Coninckx" <bart.coninckx@xxxxxxxxxx>
> To: <xen-users@xxxxxxxxxxxxxxxxxxx>
> Sent: Thursday, August 05, 2010 9:53 AM
> Subject: [Xen-users] DRBD iSCSI failover while running Xen guests
> > Hi,
> >
> > has anyone running Xen on top of iSCSI on top of a DRBD active/passive
> > cluster?
> Yes, I have two openfiler systems on drbd devices, exporting iscsi to
> xen machines using heartbeat for HA services.
> > Have you tested failovers?
> Not as I would.
> > Do Xen guests survive?
> It depends.
> A Win2000 hvm crashes (BSOD), a low load hvm linux survives
> with some messages from kernel about disks going up and down, a
> heavy load pv linux (openSUSE) works flawlessly.
> A Win2003 with pv drivers survives logging about slow disk responses.

We do the same and my experiences are similar. I haven't done a deliberate 
failover, but I do notice that Windows HVM guests are way more prone to 
corruption when ANYTHING happens to their harddisks (being in fact iSCSI 
targets). What we do as an added precaution is daily diskdumps of the guests 
OS drives, including memory state (xm save) so we can always revert to these 
states in case of catastropic failover. 
Remember DRBD is a high availability solution, not a permanent availability 
solution.  ;-)
But it works good though, especially for live migration and stuff.


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