Date: Mon, 12 Sep 2011 14:32:34 -0500 (CDT) From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> To: Laszlo KAROLYI <szoftos@freemail.hu> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS-lighttpd2-sendfile, too high IO Message-ID: <alpine.GSO.2.01.1109121428570.12948@freddy.simplesystems.org> In-Reply-To: <freemail.20110912210908.38291.2@xmldata09.freemail.hu> References: <freemail.20110912210908.38291.2@xmldata09.freemail.hu>
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On Mon, 12 Sep 2011, Laszlo KAROLYI wrote: > But does this explain the 4-5mbyte/s reads when having a 15mbit/s network load? There are only two viable explanations: o Insuffient caching due to insufficient resources o Data is not being cached at all Zfs reads whole 128K blocks (or whatever the filesystem blocksize is) at a time. It does not read partial blocks from underlying storage. This makes it very expensive to perform many small read accesses if the reads are not subsequently cached in the ARC. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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