Date: Sun, 31 Mar 2002 14:14:31 -0800 From: Kirk McKusick <mckusick@beastie.mckusick.com> To: Garance A Drosihn <drosih@rpi.edu> Cc: Alfred Perlstein <bright@mu.org>, arch@FreeBSD.ORG Subject: Re: UFS snapshots in current Message-ID: <200203312214.g2VMEWD07500@beastie.mckusick.com> In-Reply-To: Your message of "Sun, 31 Mar 2002 01:50:10 EST." <p05101537b8cc5eb19b8e@[128.113.24.47]>
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Date: Sun, 31 Mar 2002 01:50:10 -0500 To: Alfred Perlstein <bright@mu.org> From: Garance A Drosihn <drosih@rpi.edu> Subject: Re: UFS snapshots in current Cc: Kirk McKusick <mckusick@beastie.mckusick.com>, arch@FreeBSD.ORG At 8:50 PM -0800 3/30/02, Alfred Perlstein wrote: >Looks like you hit one of the snapshot deadlock conditions, >Dr McKusick recently introduced a fix for one of the >deadlocks so this may not happen again... In the past week? The "old" current system which I had been running should have been from March 26th, when I rebuilt it to see if it would fix my vmware problems (which it did...). I don't see any commits wrt softupdates which are that recent. -- Garance Alistair Drosehn = gad@eclipse.acs.rpi.edu Senior Systems Programmer or gad@freebsd.org Rensselaer Polytechnic Institute or drosih@rpi.edu All of the above is basically correct. Your use of a snapshot over a long period of time and in particular over a CVS update, build world, and install world should not cause trouble (other than perhaps a large amount of disk space being used). There is no problem with rebooting, provided that the filesystem with the snapshot is cleanly unmounted. Snapshots can be made to survive panics by setting `sysctl -w debug.dopersistence=1' but at a non-trivial performance cost. The problem that you encountered was most likely a deadlock in the snapshot code. I fixed one deadlock last January, but am aware of at least one more that is still there. I have a fairly good idea on how to fix it, but have not yet had the time to work on that fix. On your final question about making a pax archive, if you make an archive of the real filesystem, the snapshot will show up on the archive as a file the size of the filesystem partition. If you mount the snapshot and then make an archive of that filesystem, then the snapshot(s) in the archive will show up as zero length files. Kirk McKusick To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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