Date: Thu, 13 Jan 2000 11:28:21 +1100 From: Peter Jeremy <peter.jeremy@alcatel.com.au> To: "Kenneth D. Merry" <ken@kdm.org> Cc: freebsd-hardware@FreeBSD.ORG Subject: Re: hardware Message-ID: <00Jan13.112823est.40325@border.alcanet.com.au> In-Reply-To: <20000112170836.B93083@panzer.kdm.org>; from ken@kdm.org on Thu, Jan 13, 2000 at 11:01:20AM %2B1100 References: <387D0354.63159B8@ddsecurity.com.br> <72218.947717759@verdi.nethelp.no> <20000113124314.I5228@cs.waikato.ac.nz> <20000113125237.J5228@cs.waikato.ac.nz> <20000112170836.B93083@panzer.kdm.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On 2000-Jan-13 11:01:20 +1100, "Kenneth D. Merry" <ken@kdm.org> wrote: >dump is notoriously slow. I wouldn't say `notoriously', but I agree it is slower than it could be. >If a file-based backup is acceptable, you could probably get a lot better >performance by going through the filesystem. I'm not so sure. My experiences are that something like tar is significantly slower than dump (and will result is all the inodes having their atime updated). Admittedly, this will depend on the sizes and layout of the files. Some time ago (mid-November 1998), I looked into dump (check out the thread `dump(8) very slow' in freebsd-hackers). The major problem with dump is that it reads the disk in filesystem-block (typically 8K) sized blocks (or less for frags) and doesn't attempt to merge adjacent reads. It also dumps files in inode order - accessing the disk in same order as the output blocks, rather than trying to sort the disk reads. I instrumented dump to get a record of physical disk accesses whilst dumping a couple of filesystems and did some experiments with re-ordering the reads, but never posted my results (I don't remember what the results were, but I didn't get a massive speed-up). Peter To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?00Jan13.112823est.40325>