Date: Tue, 28 Sep 2010 08:45:08 -0400 From: Stephen Sanders <ssanders@softhammer.net> To: Alexander Motin <mav@FreeBSD.org> Cc: freebsd-performance@freebsd.org Subject: Re: gstripe small transaction size Message-ID: <4CA1E354.8000608@softhammer.net> In-Reply-To: <4CA180FD.9050002@FreeBSD.org> References: <mailpost.1285637728.6805046.34210.mailing.freebsd.performance@FreeBSD.cs.nctu.edu.tw> <4CA180FD.9050002@FreeBSD.org>
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Ooops, didn't put out the particulars of the system. This is a FreeBSD 8.0 system that has not been updated. We upped the block size of the da driver, not MAXPHYS. I'll give that a shot. Thanks. On 09/28/2010 01:45 AM, Alexander Motin wrote: > Stephen Sanders wrote: >> I'm trying a disk throughput experiment where in two 3ware raid 6's are >> being put into a g_strip raid 0. >> >> The raid 6's are using 8 7200RPM disks. The disk transfer rate is >> ~80MB/s. Using a load generation tool that is using O_DIRECT for I/O, >> I've generated the following short output from iostat. Needless to say, >> the write performance is a lot less than I'm expecting. >> >> We've modified the kernel such that our KB/t figure is closer to 512KB/t >> per disk when measured without the g_strip. With g_strip turned on, the >> KB/t number is more like 60KB/t. >> >> The question is how do I get g_stripe to write larger transactions to >> the disk ? > How old is your system? There was bug, fixed 8-12 months ago, making > fast mode in gstripe not working on systems with increased MAXPHYS. As I > understand, it is what you've changed in your kernel. >
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