Date: Mon, 12 Sep 2011 13:23:23 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Laszlo KAROLYI" <szoftos@freemail.hu>, <freebsd-fs@freebsd.org> Subject: Re: ZFS-lighttpd2-sendfile, too high IO Message-ID: <F959B6B4287E4B7A9C55B34E7A2EDAC9@multiplay.co.uk> References: <freemail.20110912131045.97846.1@xmldata03.freemail.hu>
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sendfile doesn't work as you might expect on zfs, its not zero copy due to the use of none buffer pool memory.
You do get a benefit but it requires double the amount of memory to get it so we've disabled sendfile
under nginx for zfs based hosts for this very reason.
Regards
Steve
----- Original Message -----
From: "Laszlo KAROLYI" <szoftos@freemail.hu>
To: <freebsd-fs@freebsd.org>
Sent: Monday, September 12, 2011 12:10 PM
Subject: ZFS-lighttpd2-sendfile, too high IO
> Hello, Recently I installed a FreeBSD with the newest 8.2-STABLE and zfs version. I use lighttpd2 and zfs on it, and munin to
> monitor the outgoing bandwidth. Zpool version 28, zfs version 5, with the latest kernel. We have a big mp3 archive (half hour,
> 256kbit/s mp3-s) which lighty serves. This means full random IO. When I see that the server serves 15mbit/sec, i see constantly
> 8-10Mbyte/sec reads on the zfs raidz1 array, which is too much. As I could see from truss logs, lighty uses sendfile and
> writev.My settings: vfs.zfs.l2c_only_size: 15106737664
...
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