Disk cloning

[Dimitri Yioulos]

On Wednesday 21 January 2009 8:11 am, Ryan Bair wrote:
> It's supposed to sync before the snapshot, yes. The whole idea is that
> the snapshot is consistent with the disk at the point in time the
> snapshot was taken which makes it leaps and bounds better than just
> running dd/rsync/tar on the raw volume. Consistent backups are the
> only reason LVM has snapshots as the current implementation is pretty
> useless for anything else.
>
> To the database it will be just like if you pulled the plug at that
> exact moment that you took the snapshot. Any database worth using
> _will_ be able to recover and continue on its merry way when you start
> up from the backup. Not so sure about MySQL though. :-)
>
> --Ryan
>
> On Wed, Jan 21, 2009 at 4:55 AM, Tino Schwarze
>
> <linux-poweredge.lists at tisc.de> wrote:
> > Hi,
> >
> > On Tue, Jan 20, 2009 at 04:35:37PM -0500, Ryan Bair wrote:
> >> Are your active volumes on LVM? If so an LVM snapshot will make this
> >> much easier. (Didn't see this mentioned yet, but it is a huge thread)
> >
> > An LVM snapshot is probably only slightly better than dd. It won't give
> > you a consistent database storage either. It might do a sync on the file
> > systems but I'm not sure.
> >
> > Tino.
> >
> > --

Hi, folks.

Catching up a bit here, after being out of the office yesterday.

Just when I think dd is the answer for my project, someone will put the kibosh 
on it, and I say that in the best possible sense.  Here's what I've been able 
to glean from the situation at hand, lots of reading, and responses on the 
list:

-- system resides in its entirety on sda
-- need faithful reproduction of sda on sdb in order to save Ensim and as DR
-- no RAID or LVM
-- down time not an option (so not able to use Clonezilla, G4L, etc.)
-- active MySQL databases
-- dd shouldn't be used on systems with open files
-- creating software RAID post-system installation may lead to data loss

Oh, oh, am I SOL here?

Dimitri

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