Date: Tue, 15 Mar 2011 17:07:20 -0500 From: Adam Vande More <amvandemore@gmail.com> To: Polytropon <freebsd@edvax.de> Cc: freebsd_user@guice.ath.cx, freebsd-questions@freebsd.org Subject: Re: IDE -- mount partitions for better performance Message-ID: <AANLkTikPiHwLLjCQVHWQTsPLVNVOkPvo%2Bx_d2Caj6UYd@mail.gmail.com> In-Reply-To: <20110315215907.f8a08352.freebsd@edvax.de> References: <8a6023db5a3d4c8b34161f7ee0af29bb.squirrel@wtp1.ath.cx> <201103151041.56373.erich@alogreentechnologies.com> <5ab7e13805185464a4adf0c5d326671e.squirrel@wtp1.ath.cx> <20110315215907.f8a08352.freebsd@edvax.de>
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On Tue, Mar 15, 2011 at 3:59 PM, Polytropon <freebsd@edvax.de> wrote: > Keep in mind that performance "across" ad0 and ad2 is best. > Masters are always good. Slaves are slower. Using primary > and secondary in parallel works good, working on a master > and a slave simultanously is worse. > Your statement about master being faster than a slave is simply not true for almost every scenario when using devices with same capabilites. All master/slave really controls is enumeration, and shouldn't effect performance in and of itself. Other variables can effect that of course, like using a slower device as an ATA Device-1 with a faster Device-0. Even that example isn't ubiquitous as many, maybe most controllers are able to support mixed devices each in their fastest mode. The whole IDE device contention really isn't much of a bottle neck in this scenario. It's only a big factor when there's *a lot* of simultaneous IO going to both, say dumping one disk to another. The highest preforming setup in something like this is likely to be something along the lines of a 4-way /boot gmirror, and a 4-way gstripe with a smaller stripe size eg 32k across the remaining usable space. If you aggregate your disk IO in this manner, IDE channel contention shouldn't be much of a bottleneck. -- Adam Vande More
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