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

[Berend de Boer]

>>>>> "Markus" == Markus Gebert <markus.gebert at hostpoint.ch> writes:

    Markus> Of course it'd be safest to EBS snapshot all disk at the
    Markus> same exact time, but if I understand you correctly, there
    Markus> is no such functionality and the OS is expected to
    Markus> guarantee some kind of consistency between multiple
    Markus> related disks.

That's exactly the point. I agree with you that the one disk solution
is trivial. It's the multiple disk case that concerns me.


    Markus> Yes, but a zfs snapshot is near instant. ioctl, wait for
    Markus> sync, mark clean, trigger EBS snapshot, ioctl again to
    Markus> resume IO, sounds like more work.

Definitely true. Could take a few seconds if you have a lot of
disks. But a hickup of can't write for a few seconds isn't noticeable
in most situations.

And after you have done your zfs snapshot, you're not done either! You
have to transfer it somewhere, probably compressed, so your (p)bzip2
dominates your CPUs, your network bandwidth is gone, etc. So a backup
starts to becomes a really high impact event, while an EBS snapshot
today isn't a big deal. Slightly degraded performance perhaps, but not
much.

--
All the best,

Berend de Boer


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