EBS snapshot backups from a FreeBSD zfs file system: zpool freeze?

[Berend de Boer]

>>>>> "Mark" == Mark Felder <feld at feld.me> writes:

    Mark> On the other hand, every time I read about "block storage
    Mark> snapshots" -- even if you quiesce the filesystem -- I start
    Mark> to get really itchy thinking about the likeliness a high TPS
    Mark> database is going to end up with corruption and require
    Mark> recovery. :)

That's not how it works: if you freeze the file system at a consistent
point, you can use the roll-forward/backward capabilities of your db
to come back clean.

You can do this even fancier. Mysql or Mongo allow you to flush their
caches as well + put in place a global lock of the database.

Then you freeze the file system, take the snapshot, unfreeze file
system, then unfreeze mysql.

People have been using this for many years, for example a famous
utility for this was mylvmbackup: http://www.lenzg.net/mylvmbackup/

ZFS should work really well here, and people probably use zfs
snapshots in this manner. If performance is an issue, you do this on
the slave obviously.


But I don't get the itchy part: if a disk is just software, I can copy
it. I want to copy it. To another data centre (zone) for
example. That's a trivial operation in EBS, and you can clone huge
disks this way in minutes. Doing an zfs send/recv is just laughably
primitive and slow compared to this. It would take me days to send a
full snapshot this way.


    Mark> This really does sound like Amazon needs to provide whatever
    Mark> mechanism to communicate between the host and the guest so
    Mark> this EBS snapshot can take place.

Again, my request has *nothing* to do with EBS. If you have multiple
disks in your pool, how can you make a backup you can restore from, at
the hardware level.

--
All the best,

Berend de Boer


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