Date: Wed, 26 Jan 2005 20:04:18 -0800 (PST) From: Arne "Wrner" <arne_woerner@yahoo.com> To: delphij@delphij.net Cc: freebsd-fs@FreeBSD.ORG Subject: Re: ufs+softupdates / consistency Message-ID: <20050127040418.26913.qmail@web41205.mail.yahoo.com> In-Reply-To: <1106796206.623.35.camel@spirit>
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--- Xin LI <delphij@frontfree.net> wrote: > 在 2005-01-26三的 17:42 -0800，Arne WXrner写道： > > Can somebody explain me, why write speed is so much slower > > than read speed (even with hard disc write cache)? > > This is common case caused by physical constraints I guess :-) > > I tried an UFS1 file system mounted async for another test. > > And the write speed was still about 5 Mbyte/sec. > > Well, I haven't benchmarked it by myself, however, the author of > SoftUpdates claims that the benchmark should be 95% or so as you > async mount a UFS file system. BTW: I think 5MB/s of write > speed is somewhat too slow for an IDE device, you may want to > check the cable, etc. > Hmm. I tried a "dd if=/dev/zero of=a bs=64k count=1000 ; sync" with KNOPPIX and the same slice/cable and ext3fs (mkfs with defaults) and it was about 4 times faster than FreeBSD R5.3. Furthermore the read speed is about 25Mbyte/sec, so that the cable seems to be ok. Funnily my other hard disc (SAMSUNG SP1604N), which uses the same cable, is much faster: write (bs=64k count=1000 if=/dev/zero): appr. 48Mbyte/sec read (bs=64k count=3975 if=<another file>): appr. 38Mbyte/sec (???????????) I do not understand this different behaviour... *sniff* -Arne __________________________________ Do you Yahoo!? Yahoo! Mail - Helps protect you from nasty viruses. http://promotions.yahoo.com/new_mail
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