Date: Sat, 23 Sep 2000 15:01:31 -0500 From: Barry Pederson <bpederson@geocities.com> To: arch@freebsd.org Subject: Re: Snapshots in the Fast Filesystem Message-ID: <39CD0C1B.324AA1C5@geocities.com> References: <200007060342.UAA23667@beastie.mckusick.com>
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Kirk McKusick wrote: > > I have completed an initial implementation of snapshots for the > fast filesystem (UFS/FFS). I have put up a tarball on > > http://people.freebsd.org/~mckusick/snap.tgz > > I am looking for comments and feedback on these changes. I am > proposing to put them into 5.0-current on Tuesday July 11th > unless I get feedback indicating that folks are not happy > with this addition. Enclosed below is the README file that > is included in the above tarball. > .................... > > So, as you can see, this is definitely alpha-quality code. > Much remains to be done to make it really useful in > production systems. But, I wanted to let folks get a chance > to try it out and start reporting bugs. I've been fooling with this in 5.0-CURRENT, and have have found it to be a terribly, terribly cool feature. In trying to setup some scripts to automatically take snapshots on a daily basis, I came up with a few questions... Is there (or will there be) some way to get a list of snapshots that have been created on a filesystem? Kirk suggests following a convention for naming snapshot files, but if that doesn't happen for some reason, it would be good to have some foolproof way of determining what snaps exist. Otherwise, I suppose you could search a filesystem for files that -appear- to be almost as large as the filesystem itself, but that seems kind of a kludge - and I don't know if I'd want to trust a script to interpret those results correctly. Since snapshots can be mounted using vn devices, I was similarly wondering if there's a good way of determining if a particular vn device is already configured, and if so, which particular file it's using. (man vnconfig didn't seem to mention anything like this) (it seems to me that if you can create and configure 'things' in the OS, there should be some way to discover what's been created and/or how things have been configured) Kirk gives the example of mounting a snapshot by using a 'vn0c' device - I was wondering if the 'c' part of those device names is significant? Could you mount additional snapshots using 'vn0a', 'vn0b' and so on? or should a person stick to creating and using (as I've tried and found to work well) 'vn1c', 'vn2c', and so on? (That may be a bit of a newbie-unix question, but since I was asking about snapshots I thought I'd throw it out). Lastly, I'm curious if it's possible that snapshots will be MFC'd into 4.x at some point? or will this be a 5.0 and up only feature? Barry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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