Date: Mon, 9 May 2005 14:50:14 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Amandeep <aman@chamkila.org> Cc: john@essenz.com Subject: Re: Low HDD tranfer rate with FreeBSD 5.3-Release Message-ID: <20050509195011.GH38839@dan.emsphone.com> In-Reply-To: <427FBD12.2090101@chamkila.org> References: <427FA802.90805@chamkila.org> <427FA8CD.8040405@centtech.com> <427FAB5F.6070508@chamkila.org> <427FAF73.7070702@centtech.com> <20050509190245.GF38839@dan.emsphone.com> <427FB663.3090309@chamkila.org> <427FBD12.2090101@chamkila.org>
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In the last episode (May 09), Amandeep said: > Amandeep wrote: > >>>>>>The transfer rate is about 15MB/s > >>>>>> > >>>>>>when I run > >>>>>>#dd if=/dev/zero of=/usr/junk bs=8192 > > > >OK with the above dd > > > >dd if=/dev/ad0 of=/dev/null bs=64k > > > >it gives me 56MB/s. from the start. > > So how does the block size makes the difference?? What is the true > transfer rate.? At the moment, 56MB/sec :) Those two speeds aren't directly comparable, since your first was testing writes through the filesystem with a small blocksize, and the second was testing reads to the raw device with a large blocksize. Usually reading, using raw devices, and using large blocksizes are faster then writing, using a filesystem, and using small blocksizes, so all three changes probably contributed a little to the speed difference. -- Dan Nelson dnelson@allantgroup.com
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