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Re: [Xen-users] Re: Backup

To: "Robert Dunkley" <Robert@xxxxxxxxx>
Subject: Re: [Xen-users] Re: Backup
From: "Paras pradhan" <pradhanparas@xxxxxxxxx>
Date: Thu, 20 Nov 2008 09:22:56 -0600
Cc: Ferenc Wagner <wferi@xxxxxxx>, Xen Users <xen-users@xxxxxxxxxxxxxxxxxxx>
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On Thu, Nov 20, 2008 at 7:45 AM, Robert Dunkley <Robert@xxxxxxxxx> wrote:
Hi Paras,

I'm not sure if your question was performance related but if your
storage system is local then you should see about 50Mbytes/second on a
single 7200RPM SATA disk or about 100Mbytes/sec for a single 15000Rpm
SAS drive; assuming they have very little disk activity from other VMs.
Raid 0 and Raid 5 arrays should be an order of magnitude faster.  So
speed wise that 9Mbytes/second looks too low.


-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Ferenc
Sent: 20 November 2008 13:41
To: Paras pradhan
Cc: Xen Users
Subject: [Xen-users] Re: Backup

"Paras pradhan" <pradhanparas@xxxxxxxxx> writes:

> Here's what I did:
> To backup:
> 1) Saved the virtual machines' state using:
> xm save guest01 /guest01.save
> 2) lvcreate -s -L 2G -n guest01-snap /dev/vg/guest01-disk
> 3) Restored the VM
> xm restore /guest01.save
> 4) Used DD to create the image
> dd if=/dev/vg/guest01-snap of=/guest01.img
> 5) lvremove /dev/vg/guest01-snap
> To restore:
> 1) I turned off the VM (i don't like this)
> xm shutdown guest01
> 2) Then run:
> dd if=/guest01.img of=/dev/vg/guest01-disk
> 3) Turn back the VM on
> --
> My virtual machine is consuming 11GB of space. Now when i do DD while
> restoring it took a lot of time.
> ---
> 10737418240 bytes (11 GB) copied, 1189.42 seconds, 9.0 MB/s
> ---
> Is this normal?

Impossible to tell without knowing a lots of details about your
storage system.

> I don't know if the process that I have used is fine or not. Need
> views on this.

Looks OK, but be prepared that your filesystems will be unclean after
restore.  If instead of turning the VM on you did an xm restore again,
then your filesystems would be OK, but some operations could be carried
out again in the restored domain.

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As recommended  by agent, I have tested/restored with bs=4096 and now i am getting around 35mb/s in my 7200 RPM SATA drive. It works for me but still it should be more than that I guess.

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