Date: Wed, 3 Jul 2013 16:02:41 -0400 From: Gary Palmer <gpalmer@freebsd.org> To: Berend de Boer <berend@pobox.com> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: EBS snapshot backups from a FreeBSD zfs file system: zpool freeze? Message-ID: <20130703200241.GB60515@in-addr.com> In-Reply-To: <87mwq34emp.wl%berend@pobox.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> <871u7g57rl.wl%berend@pobox.com> <op.wznad7th34t2sn@tech304.office.supranet.net> <87mwq34emp.wl%berend@pobox.com>
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On Thu, Jul 04, 2013 at 07:39:26AM +1200, Berend de Boer wrote: > 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. Other than using SAN (FC or iSCSI), I know of no reason to do backups at the raw disk level, nor any real demand. I've worked with people who have done LUN based backups in the past and they have one drawback - they tend to back up the entire LUN, irrespective of whether it is an allocated block or not. Modern systems that implement some kind of TRIM emulation (or cheat and sniff the filesystem block allocation maps) may alleviate that problem. However, in the vast majority of cases, people back up from above the FS, not below. This makes your use case probably more tied to EBS than you may otherwise think. Regards, Gary
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