Date: Fri, 22 Jul 2005 11:25:40 -0500 (CDT) From: Chris Dillon <cdillon@wolves.k12.mo.us> To: Eric Anderson <anderson@centtech.com> Cc: freebsd-fs@freebsd.org Subject: Re: mksnap_ffs takes 4-5 minutes? Message-ID: <20050722111015.P25012@duey.wolves.k12.mo.us> In-Reply-To: <42E0E39E.8020009@centtech.com> References: <42DD64AB.3000605@centtech.com> <20050720094830.GR782@marvin.riggiland.au> <42DE3C1F.9070704@centtech.com> <20050720130523.GT782@marvin.riggiland.au> <42E0E39E.8020009@centtech.com>
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On Fri, 22 Jul 2005, Eric Anderson wrote: > The snap seemed to suspend the filesystem nearly immediately, and > kept it suspended for quite some time - I would say probably more > than half the time. In order for snapshots to be very useful, it > must work on large filesystems (100GB+) in a reasonable amount of > time (a few seconds would be ok). I know for certain that one test > filesystem (2Tb) had nothing on it, no processess using the > filesystem at all, and it took well over an hour to run mksnap on > it. Just another datapoint -- I take daily snapshots of a 270GB filesystem and it takes 3 to 4 minutes (not sure down to the second). I used to take multiple snapshots during the day but suspending the filesystem for several minutes at peak times wasn't working out (and seemed to cause complete system hangs, sometimes), so I just went to once per day during off-hours. Making the snapshots seems to be mostly I/O bound, and this is on a system with a fairly fast RAID5 array of 10KRPM SCSI drives. The suspension of the filesystem also seems immediate to me, so it seems most of the time is actually spent making the snapshot. Filesystem 1K-blocks Used Avail Capacity iused ifree %iused Mounted on /dev/da1s1a 272092768 16863968 233461380 7% 155146 8435700 2% /userspace Jul 20 00:14:11 rshome root: snapshot: daily.0 snapshot on filesystem /userspace made (duration: 4 min) Jul 21 00:14:01 rshome root: snapshot: daily.0 snapshot on filesystem /userspace made (duration: 3 min) Jul 22 00:14:04 rshome root: snapshot: daily.0 snapshot on filesystem /userspace made (duration: 4 min) I'm using Ralf S. Engelschall's snapshot management scripts, though I know that has no effect on the time it takes to create a snapshot. -- Chris Dillon - cdillon(at)wolves.k12.mo.us FreeBSD: The fastest, most open, and most stable OS on the planet - Available for IA32, IA64, AMD64, PC98, Alpha, and UltraSPARC architectures - PowerPC, ARM, MIPS, and S/390 under development - http://www.freebsd.org Q: Because it reverses the logical flow of conversation. A: Why is putting a reply at the top of the message frowned upon?
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