[Linux-cluster] Snapshotting GFS and freezing

Dirk H. Schulz dirk.schulz at kinzesberg.de
Sat Jan 23 10:12:54 UTC 2010

Ray Van Dolson schrieb:
> On Wed, Jan 20, 2010 at 06:14:02AM -0800, Dirk H. Schulz wrote:
>> That means calling
>>         sync
>>         echo 3 > /proc/sys/vm/drop_caches
>> inside the VM, right? Or is there anything more to do to flush everything?
>> Dirk
> I would think the best way would be to actually pause the VM.  If you
> snapshot a VM while it's running, even with the above, how can you
> guarantee an application won't do something on the VM right as the
> snapshot occurs?

That is an important point, I am already pondering about it. Of course 
pausing the vm is the better option - if you can afford it.

I am working systematically on an environment where the possibility of 
very high level availability vms is part of the design (e.g. 99,99 %). 
At the moment the only approach I can see is doing snapshots of a 
running vm and making those as reliable as possible.


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