Date: Mon, 31 Mar 2008 21:51:20 +0200 From: "Ivan Voras" <ivoras@freebsd.org> To: d@delphij.net Cc: freebsd-current@freebsd.org Subject: Re: Are large RAID stripe sizes useful with FreeBSD? Message-ID: <9bbcef730803311251l79af84b1j7a3a8018442a6478@mail.gmail.com> In-Reply-To: <47F133AE.2010900@delphij.net> References: <fsr7fb$hl0$1@ger.gmane.org> <47F133AE.2010900@delphij.net>
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On 31/03/2008, Xin LI <delphij@delphij.net> wrote: > Ivan Voras wrote: > > Most of new hardware RAID controllers offer stripe sizes of 128K, 256K > > and some also have 512K and 1M stripes. In the simplest case of RAID0 of > > two drives, knowing that the data is striped across the drives and that > > FreeBSD issues IO request of at most 64K, is it useful to set stripe > > sizes to anything larger than 32K? I suppose something like TCQ would > > help the situation but does anyone know how is this situation usually > > handled on the RAID controllers? > > Short answer: yes. Larger stripe sizes would allow better performance > for continuous read/write. In theory they will negatively affect small > size read/write but in practice you will notice that larger stripe size > would give better performance in almost all cases. Ok, I'm interested in how it works. Are the IO requests queued at the controller until there's enough of them to write a stripe block?
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