Date: Tue, 10 Oct 2006 01:52:05 +0200 From: Fluffles <etc@fluffles.net> To: freebsd-fs@FreeBSD.org Subject: Re: 2 bonnies can stop disk activity permanently Message-ID: <452AE0A5.3010503@fluffles.net>
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Bruce Evans wrote: >I suspect the problems are that the 64K-block i/o is usually perfectly >misaligned unless the fs itself has 64K-blocks and the fs's partition >starts on a 64K-block boundary, and that some hardware or firmware >(mainly RAIDs) want the blocks to be aligned. But i have done these tests on /dev/da0, thus without any labeling! This means there is no offset such as 16 sectors caused by disk labeling, which then spoils my stripe-block. So i would assume there is no alignment problem, is there? I would assume that if i do newfs directly on /dev/da0, that the 64KB blocksize starts at offset 0, which implies no alignment problems exist. If all this is true, another reason for the huge performance increase must be sought. In all my tests using 64KB blocksize instead of the default 16KB yielded better results; also with software RAID like gstripe. And i never use labeling. Actually i would have liked the blocksize limit to be higher, and try out if 128KB or even higher would continue to yield better results. - Veronica
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