Date: Sun, 31 Oct 2010 13:12:26 -0700 From: perryh@pluto.rain.com To: dillon@apollo.backplane.com Cc: cronfy@gmail.com, freebsd-hackers@freebsd.org Subject: Re: Slow disk access while rsync - what should I tune? Message-ID: <4ccdcdaa.XSDkZZUUYXDXpkXV%perryh@pluto.rain.com> In-Reply-To: <201010311635.o9VGZG1O046164@apollo.backplane.com> References: <AANLkTikzZvZn=vNNRtcSViWq8ty7b8qOooQ4NbHiJH5q@mail.gmail.com> <AANLkTikpk4O-q_Omh9eAGZB474J1BVu2YJ7OKWvhZm7v@mail.gmail.com> <4ccceb10.4n2iAQ/sY/YrDSI2%perryh@pluto.rain.com> <201010311635.o9VGZG1O046164@apollo.backplane.com>
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[missing attribution restored] Matthew Dillon <dillon@apollo.backplane.com> wrote: > perryh@pluto.rain.com wrote: > :cronfy <cronfy@gmail.com> wrote: > : > :> And also, maybe there are other ways to create incremental backups > :> instead of using rsync/hardlinks? > : > :Yes. Use dump(8) -- that's what it's for. It reads the inodes, > :directories, and files directly from the disk device, thereby > :eliminating stat() overhead entirely. > : > :Any replication mechanism -- rsync, tar, even dd -- can be used > :as a backup mechanism, but dump was specifically designed for the > :purpose. > Well, dump is 25+ years old ... Why are you running BSD if you prefer newer (=> less mature) stuff? Switch to Linux! > ... On a modern (large) filesystem you are virtually guaranteed > to get corruption due to the asynchronous nature of the dump. > > This can be partially mitigated by using a block level snapshot on > the UFS source filesystem and then dumping the snapshot instead of > the live filesystem ... IOW by using "dump -L" > Plus dump uses mtime to detect changes, which is unreliable, ... Are you sure about that? Last I knew it used ctime. > and the output produced by dump is not live-accessible whereas a > snapshot / live filesystem copy is. That makes the dump fairly > worthless for anything other than catastrophic recovery. Ever heard of "restore -i"?
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