Date: Thu, 11 Jan 2007 13:40:12 -0800 From: Scott Oertel <freebsd@scottevil.com> To: Kris Kennaway <kris@obsecurity.org> Cc: Willem Jan Withagen <wjw@digiware.nl>, freebsd-stable@freebsd.org Subject: Re: running mksnap_ffs Message-ID: <45A6AEBC.800@scottevil.com> In-Reply-To: <20070111200152.GA36123@xor.obsecurity.org> References: <459ABB40.7050603@digiware.nl> <20070111153651.GC31382@xor.obsecurity.org> <45A68F2E.6040205@scottevil.com> <20070111200152.GA36123@xor.obsecurity.org>
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Kris Kennaway wrote: > On Thu, Jan 11, 2007 at 11:25:34AM -0800, Scott Oertel wrote: > >> Kris Kennaway wrote: >> >>> On Tue, Jan 02, 2007 at 09:06:24PM +0100, Willem Jan Withagen wrote: >>> >>> >>>> Hi, >>>> >>>> I got the following Filesystem: >>>> Filesystem Size Used Avail Capacity iused ifree %iused >>>> /dev/da0a 1.3T 422G 823G 34% 565952 182833470 0% >>>> >>>> Running of a 3ware 9550, on a dual core Opteron 242 with 1Gb. >>>> The system is used as SMB/NFS server for my other systems here. >>>> >>>> I would like to make weekly snapshots, but manually running mksnap_ffs >>>> freezes access to the disk (I sort of expected that) but the process >>>> never terminates. So I let is sit overnight, but looking a gstat did not >>>> reveil any activity what so ever... >>>> The disk was not released, mksnap_ffs could not be terminated. >>>> And things resulted in me rebooting the system. >>>> >>>> So: >>>> - How long should I expect making a snapshot to take: >>>> 5, 15, 30min, 1, 2 hour or even more??? >>>> >>>> >>> Yes :) Snapshots were not designed for use in this way (they were >>> designed to support background fsck and allow faster system recovery >>> after power failure), so they don't scale as well as you might like on >>> large filesystems. >>> >>> Kris >>> >>> >> If snapshots were designed to support background fsck, then why did they >> not make it more scalable? If you can't create a snapshot without the >> system locking up, that means fsck won't be able to either, making >> background fsck worthless for systems with large storage. >> > > locking up != taking a long time to complete. You haven't > differentiated between those two situations yet. > > Kris > It depends, sometimes it just takes a really long time during which the system is unresponsive and unstable, or it just completely locks up. Does it make that much of a difference? in either case, snapshotting large drives is not very efficient, and can't be considered for background fsck, or daily backup. Which are the two main purposes of snapshots. --Scott
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