Date: Wed, 03 Jul 2013 23:21:23 +1200 From: Berend de Boer <berend@pobox.com> To: Markus Gebert <markus.gebert@hostpoint.ch> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: EBS snapshot backups from a FreeBSD zfs file system: zpool freeze? Message-ID: <87ppuz51os.wl%berend@pobox.com> In-Reply-To: <FF386ED5-5E9D-4073-9E67-F835BCF5D816@hostpoint.ch> 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> <14A2336A-969C-4A13-9EFA-C0C42A12039F@hostpoint.ch> <87zju43sxl.wl%berend@pobox.com> <FF386ED5-5E9D-4073-9E67-F835BCF5D816@hostpoint.ch>
next in thread | previous in thread | raw e-mail | index | archive | help
--pgp-sign-Multipart_Wed_Jul__3_23:21:23_2013-1
Content-Type: text/plain; charset=US-ASCII
>>>>> "Markus" == Markus Gebert <markus.gebert@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
------------------------------------------------------
Awesome Drupal hosting: https://www.xplainhosting.com/
--pgp-sign-Multipart_Wed_Jul__3_23:21:23_2013-1
Content-Type: application/pgp-signature
Content-Transfer-Encoding: 7bit
Content-Description: OpenPGP Digital Signature
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.17 (GNU/Linux)
iQIcBAABCAAGBQJR1AkzAAoJEKOfeD48G3g5guQP+wcyXSEU4hWRFqmft5NmzSZq
8O/cAyAbJruyhVViMuEQFT/zgVCAhhDNt/HwQMJWIgNdyiRkX+p+jg6RqwQ4Q7tZ
I8jLfMxHQhUYJhE59Vh5wfw6syPvqOjeoDpY04mfLZ8E2JfVNiibJGAWkxCRagIj
IBm4HGSbxgrgD3ZR4WIdZpkY8ZeStL4NyeIPcbiu3aJzzAoW21fPkiCXZJ7eQ3Fx
g9SkyhhF95+A8CShhsz/QzzYGniGAoPWd1vNJ8P8dL1A3FPRgqh3u+OKj4F3jBvq
0+S1iu4mNBik8o8I7lYa5LxDx9ydHaKNwcLBStkHySGiK4snHCKRWj6bMBdHgTP7
JHe679Hdf70ik2unbWO+tnh/Hh93NsR9OsIDcr6Zep+QUJHANQe6XUV3Or/7N+xD
fY1GVnR6yq0YRKtoCk3pAfwNivKNO/9iT0CPvb3eZ3b3dc2zjtKs7hPcff8mou2l
BZpRmlusN8u4BQDg799G9y8do01bef0T32E7NJYqNj0pqrbHjg12l7Wq3xBCFwyt
F2oU8BT4UXA2rNXnz4+P0sjNm7hKR7paAsZmh/2PJDC+8FBAyiDVbBVrId1MF7tr
w+VUBqHITSUlnsO1dctj3M18zc1GypCWgL7F+eWAnptyz9+gHn+AoFWBeyGzdFex
dPKQwscCfcIgDENKBUc7
=SrOz
-----END PGP SIGNATURE-----
--pgp-sign-Multipart_Wed_Jul__3_23:21:23_2013-1--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?87ppuz51os.wl%berend>