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Re: [Xen-users] Re: 100% safe way to backup domU: (was Yet another backu

To: xen-users@xxxxxxxxxxxxxxxxxxx, Ligesh <myself@xxxxxxxxxx>
Subject: Re: [Xen-users] Re: 100% safe way to backup domU: (was Yet another backup)
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Thu, 11 Jan 2007 20:50:01 +0000
Cc: Ulrich Windl <ulrich.windl@xxxxxxxxxxxxxxxxxxxx>, Roger Lucas <roger@xxxxxxxxxxxxx>
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>  I forgot about the 'save' feature. If we have a consistent file system
> that can be mounted and backed up, and if we add the ram separately, the we
> have the entire state of the system. So I think the actual steps would be.
>
>  xm sync-and-save domU file
>  take lvm snapshot
>  xm restore file
>  backup snapshot + file

Seems like it ought to work...

I don't think you actually need to sync in the guest if you're doing this, 
though.  You'll have all the dirty buffers in the save image anyhow, so 
flushing them to disk doesn't seem necessary.

The only problem with this is it's not truly live, since you have to suspend 
the guest, it's just low downtime.

A proper solution which doesn't require a restore (and possibly which didn't 
require stopping the guest for most of the saving process) would be nicer.  
The checkpoint patches posted at least to the first half of this, although 
I'm not sure if the guest has to be paused whilst saving memory state.

>   Backing up the all the domUs live from the dom0 is an extremely important
> feature. In the hosting industry, taking down the server for getting a task
> done is not an idea that people can even understand, let alone accept.

Yep.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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