Date: Tue, 15 Jan 2013 22:54:22 +0100 (CET) From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> To: Karim Fodil-Lemelin <fodillemlinkarim@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: IBM blade server abysmal disk write performances Message-ID: <alpine.BSF.2.00.1301152251530.2950@wojtek.tensor.gdynia.pl> In-Reply-To: <50F5BC08.1060700@gmail.com> References: <CAA3ZYrACHLU-4OyhLdD%2BmfCDR_kubBg-AiVcopL-skqDurE7YA@mail.gmail.com> <50F5BC08.1060700@gmail.com>
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> > # dd if=/dev/zero of=foo count=1 bs=10240000 > 1+0 records in > 1+0 records out > 10240000 bytes transferred in 19.579077 secs (523007 bytes/sec) > you write to file not device, so it will be clustered anyway by FreeBSD. 128kB by default, more if you put options MAXPHYS=... in kernel config and recompile. Even with hard drive write cache disabled, it should about one write per revolution but seems to do 4 writes per second. so probably it is not that but much worse failure. Did you rest read speed? dd if=/dev/disk of=/dev/null bs=512 dd if=/dev/disk of=/dev/null bs=4k dd if=/dev/disk of=/dev/null bs=128k ?
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