Date: Fri, 26 Jan 2007 18:33:39 +0100 (CET) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-current@FreeBSD.ORG, roberthuff@rcn.com Subject: Re: Interesting speed benchmarks Message-ID: <200701261733.l0QHXdY1078259@lurza.secnetix.de> In-Reply-To: <17850.11127.944124.276290@jerusalem.litteratus.org>
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Robert Huff wrote: > As long as we're on the subject: > I'm testing a USB-connected external hard drive (PATA-133) as a > replacement for SCSI-I/DLT in a dump-driven backup arrangement for a > P4/2.25 ghz+80 mbyte/sec SCSI box. > [...] > Performance, so far, has been better than the old set-up but far > less than thrilling and I'd like to understand why. Dump, using > these options: > > $DUMP_LEVEL -D $DUMPDATES_FILE -Lau -f > > gets me 2 +/- 0.2 mbytes/sec. > Is this a reasonable value? (I.e. is dump the limiting > factor?) Do I need to reconfigure something, or is my hardware just > lame? > I'm not expecting to get the full 40 mbyte/sec of USB 2.0 spec; > 20 or even 10 would be fine. But 2? Ouch. Historically the performance of dump(8) has always been quite bad. It didn't matter in ancient times because tape drives were slow back then, so dump(8) was not the limiting factor. ;-) For that reason I try to avoid dump(8) when possible. Maybe you should try to use tar, cpio or pax instead and check if the performance is better. I'm not sure if dump(8) has been improved recently (I confess that I haven't tried). Maybe it is better now. If you continue to use dump(8), make sure that you specify a reasonable cache size (-C option). Refer to the manual page for details. Without that option, performance will be _really_ bad. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, USt-Id: DE204219783 Any opinions expressed in this message are personal to the author and may not necessarily reflect the opinions of secnetix GmbH & Co KG in any way. FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd It's trivial to make fun of Microsoft products, but it takes a real man to make them work, and a God to make them do anything useful.
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