Date: Sun, 27 Dec 2009 15:25:35 -1000 (HST) From: Jeff Roberson <jroberson@jroberson.net> To: patpro <patpro@patpro.net> Cc: freebsd-fs@freebsd.org Subject: Re: snapshot implementation Message-ID: <alpine.BSF.2.00.0912271525000.1027@desktop> In-Reply-To: <3ea87f5f62bb8ba30d798d4605a64c83@localhost> References: <32CA2B73-3412-49DD-9401-4773CC73BED0@patpro.net> <alpine.GSO.2.01.0912231031450.1586@freddy.simplesystems.org> <4B3283F2.7060804@barryp.org> <3ea87f5f62bb8ba30d798d4605a64c83@localhost>
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On Fri, 25 Dec 2009, patpro wrote: > > On Wed, 23 Dec 2009 14:56:18 -0600, Barry Pederson <bp@barryp.org> wrote: >> "...there's virtually no overhead at all due to the copy-on-write >> architecture. In fact, sometimes it is faster to take a snapshot rather >> than free the blocks containing the old data!" >> >> That's certainly not the case with UFS snapshots, which can take a long >> time to complete (we're talking freezing your machine's disk activity >> for many minutes), and are limited to 20 total. > > > UFS uses copy on write. But you say many minutes to complete? Don't you > speak about dump(1), that uses snapshot as a basis to dump a live file > system? > I agree, UFS snapshot creation is not lightning-fast, but many minutes > seems a lot to me, and I never experienced such a long creation time. It can take some time depending on fs activity on the machine. There are ways to continue to optimize it within the existing infrastructure. It only requires someone willing to expend the time. Jeff > > patpro > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" >
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