Date: Wed, 16 Jan 2013 08:20:13 +0100 (CET) From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> To: Dieter BSD <dieterbsd@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: IBM blade server abysmal disk write performances Message-ID: <alpine.BSF.2.00.1301160819520.4559@wojtek.tensor.gdynia.pl> In-Reply-To: <CAA3ZYrANmX=ixNrUag41%2Bbkyp=HTROfE3DscBWSiew00qB4eqg@mail.gmail.com> References: <CAA3ZYrANmX=ixNrUag41%2Bbkyp=HTROfE3DscBWSiew00qB4eqg@mail.gmail.com>
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>> The kernel must be doing write-behind even to a raw disk, otherwise >> waiting for write(2) to return before issuing the next write would >> slow it down as Matthew suggests. > > And a minute after hitting send, I remembered that FreeBSD does not > provide the traditional "raw" disk devices, e.g. /dev/rda0 with an 'r'. > (Now if I could just remember *why* it doesn't.) because they are only raw devices. caching is in filesystem.
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