On 7/11/07, Darren J Moffat <[EMAIL PROTECTED]> wrote:
> Mike Gerdts wrote:
> > Perhaps a better approach is to create a pseudo file system that looks like:
> >
> > <mntpt>/pool
> > /@@
> > /@today
> > /@yesterday
> > /fs
> > /@@
> > /@2007-06-01
> > /otherfs
> > /@@
>
> How is this different from cd <mntpt>/.zfs/snapshot/ ?
>
<mntpt>/.zfs/snapshot provides file-level access to the contents of
the snapshot. If you back those up, then restore every snapshot, you
will potentially be using way more disk space.
What I am proposing is that "cat mntpt/pool/@snap1" delivers a data
stream corresponding to the output of "zfs send" and that "cat
mntpnt/pool/@[EMAIL PROTECTED]" delivers a data stream corresponding to "zfs
send -i snap1 snap2".
This would allow existing backup tools to perform block level
incremental backups. Assuming that writing to the various files is
the equivalent of the corresponding "zfs receive" commands, it
provides for block level restores that preserve space efficiency as
well.
Why?
Suppose I have a server with 50 full root zones on it. Each zone has
a zonepath at /zones/<zonename> that is about 8 GB. This implies that
I need 400 GB just for zone paths. Using ZFS clones, I can likely
trim that down to far less than 100 and probably less than 20. I
can't trim it down that far if I don't have a way to restore the
system.
This "restore problem" is my key worry in deploying ZFS in the area
where I see it as most beneficial. Another solution that would deal
with the same problem is block-level deduplication. So far my queries
in this area have been met with silence.
Hmmm... I just ran into another snag with this. I had been assuming
that clones and snapshots were more closely related. But when I tried
to send the differences between the source of a clone and a snapshot
within that clone I got this message:
incremental source must be in same filesystem
usage:
send [-i <snapshot>] <snapshot>
Mike
--
Mike Gerdts
http://mgerdts.blogspot.com/
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
