Date: Mon, 14 Nov 2005 01:07:15 +0800 From: Xin LI <delphij@gmail.com> To: Scott Long <scottl@samsco.org> Cc: freebsd-fs@freebsd.org, user <user@dhp.com> Subject: Re: UFS2 snapshots on large filesystems Message-ID: <a78074950511130907g24c079c4gccd6c1d750d244da@mail.gmail.com> In-Reply-To: <436BDB99.5060907@samsco.org> References: <Pine.LNX.4.21.0511041531210.8180-100000@shell.dhp.com> <436BDB99.5060907@samsco.org>
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On 11/5/05, Scott Long <scottl@samsco.org> wrote: > The UFS snapshot code was written at a time when disks were typically > around 4-9GB in size, not 400GB in size =-) Unfortunately, the amount s/size/cylinder groups/g :-) > of time it takes to do the initial snapshot bookkeeping scales linearly > with the size of the drive, and many people have reported that it takes > considerable amount of time (anywhere from several minutes to several > dozen minutes) on large drives/arrays like you describe. So, you should > test and plan accordingly if you are interested in using them. I have some ideas about lazy snapshotting. But unfortunately I don't have much time to implement a prototype ATM, and I think we really need a file system that is capable for: - Handling large number of files in one directory (say, some sort of indexing mechanism, etc. And yes, I know that this is somewhat insane, but the [ab]use is present in many large e-mail systems that uses mailbox) - Effective recovery. Personally I do not buy journalling much, and I think the problem could be resolved by something like WAFL did. I think that JUFS would provide some help for (2), do you have some plan about (1)? Cheers, -- Xin LI <delphij@delphij.net> http://www.delphij.net
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