Rudi Ahlers sent a missive on 2010-02-07:
>> 2010/2/5 Simon Billis <simon@xxxxxxxxxx>
>> Do you have any shared storage that you're using which supports
>> snapshots? If you do, then a combination of coalescing the running VM's
>> to disk and taking a snap and also using traditional backup methods
>> (application aware) to disk/tape for archival and complete failure of
>> the storage is a reasonable thing to do.
>
> the main problem with this, is that one client on that VM (think about
> shared hosting accounts on the VM) wants to restore a single file, or
> a few files, then you're going to have to restore the whole snapshot
> and a lot of other files will be lost.
Not necessarily, some storage will allow the mounting of a snap as readonly
specifically to allow for this type of restore. The storage will also allow
for the snap to be R/W or duplicated and to be allocated to another host to
become a live machine.
> I'm experimenting with an NFS mount from our backup server. Basically,
> export the NFS share, and mount it inside the VM, then use your
> favorite backup procedure / software. For our cPanel VM's, we use
> cPanel's native backup function which makes use of rsync - and allows
> us to restore a single file if needed. For other VM's without a
> control panel, rsync also works well.
I've had mixed results with NFS, sometimes under high loading it would fail
and usually when I was in the process of backing up a few machines (four or
more) at once to the NFS server.
Good quality storage (which usually comes at a price) will provide the
functionality that is needed to backup the VM's either as a complete VM
image or files from the VM filesystem. Entry level storage from suppliers
such as Equallogic/Dell comes with this functionality and it is possible to
have the storage up and attached to servers within 10 mins from un-boxing it
(but do allow a little longer to understand it ;-) .)
I do believe that all backup strategies need to be examined frequently to
ensure that they have met and are meeting your needs as the requirement
often changes when new applications are rolled out or the usage of an
existing application changes.
S.
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