Date: Sun, 7 Jan 2007 23:19:23 -0500 From: David Gilbert <dgilbert@dclg.ca> To: Dan Nelson <dnelson@allantgroup.com> Cc: freebsd-hackers@freebsd.org, David Gilbert <dgilbert@dclg.ca> Subject: Re: dump reads more than restore writes? Message-ID: <17825.50763.781656.393704@canoe.dclg.ca> In-Reply-To: <20070108033046.GA41724@dan.emsphone.com> References: <17825.44456.556954.545497@canoe.dclg.ca> <20070108033046.GA41724@dan.emsphone.com>
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>>>>> "Dan" == Dan Nelson <dnelson@allantgroup.com> writes: Dan> If you have a lot of small files, dump may be rereading directory Dan> information. Dump has a cache option that can help, but make Dan> sure you also dump a snapshot (i.e. always use -L when using -C). Several people have suggested this, but actually it has the same behaviour when using -C (I often use -C 32). This filesystem is not mounted, so -L is not required, but I do use -L when required. But the filesystem is 95% full (aren't they all) and the vast majority of the files on it are "media" files --- ie: movies, mp3's, ISOs, etc. Very few files under a meg. Probably not too many files over 100 meg as most of the files on the disk are in rar format. ... now Azurus (used to obtain most of the files) writes holey files. One chunk at a time (512k-ish to 4meg-ish). Those could end up being not-very-contiguous, but I'd expect them to consist (by majority) of full filesystem blocks. The amazing part (to me) is how consistent it is. If this is not a reporting error of gstat, it makes dump look _very_ wasteful. If the numbers are being reported correctly, it means that dump is reading 600 gig to copy a 200 gig disk. !?! Dave. -- ============================================================================ |David Gilbert, Independent Contractor. | Two things can be | |Mail: dave@daveg.ca | equal if and only if they | |http://daveg.ca | are precisely opposite. | =========================================================GLO================
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