Date: Wed, 03 Jul 2013 21:10:06 +1200 From: Berend de Boer <berend@pobox.com> To: Kevin Day <toasty@dragondata.com> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: EBS snapshot backups from a FreeBSD zfs file system: zpool freeze? Message-ID: <871u7g57rl.wl%berend@pobox.com> In-Reply-To: <A5A66641-5EF9-454E-A767-009480EE404E@dragondata.com> References: <87li5o5tz2.wl%berend@pobox.com> <CA%2BtpaK1jQuKneQsxkVfxJGzXdPdLZfqBM1QWQ0e19nK5t71t1Q@mail.gmail.com> <87ehbg5raq.wl%berend@pobox.com> <20130703055047.GA54853@icarus.home.lan> <6488DECC-2455-4E92-B432-C39490D18484@dragondata.com> <CADBaqmihCB5JP01hLwXTWHoZiJJ5-jkT-Ro=oDwOcKZT_zvEKA@mail.gmail.com> <A5A66641-5EF9-454E-A767-009480EE404E@dragondata.com>
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>>>>> "Kevin" == Kevin Day <toasty@dragondata.com> writes:
Kevin> I know this is a sort of obscure use case, but Linux and
Kevin> Windows both have this functionality that VMWare will use
Kevin> if present (and the guest tools know about it).
May I correct you? This is not obscure. This is an extremely common
use-case on Linux, either using LVM/XFS file systems, and definitely
best practice on Amazon AWS. If you're not doing it this way, you're
doing it wrong.
Kevin> Linux goes a step further and ensures that it's not in the
Kevin> middle of writing anything to swap during the quiesce
Kevin> period, too. I don't think this would be terribly difficult
Kevin> to implement, a hook somewhere along the write chain that
Kevin> blocks (or queues up) anything trying to write until the
Kevin> unfreeze comes along, but I'm guessing there are all sorts
Kevin> of deadlock opportunities here.
Kevin> Either way, I'm not asking that anyone spend time to write
Kevin> this, I'm just trying to reword what the original requestor
Kevin> was talking about.
Heh, I'm asking that actually :-)
Would be great to have this in FreeBSD. Once you have used EBS
snapshots, you really don't want to go back.
--
All the best,
Berend de Boer
------------------------------------------------------
Awesome Drupal hosting: https://www.xplainhosting.com/
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