Date: Thu, 30 Sep 2010 08:58:44 -0400 From: Stephen Sanders <ssanders@softhammer.net> To: freebsd-performance@freebsd.org Subject: Re: gstripe small transaction size Message-ID: <4CA48984.5030403@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>
next in thread | previous in thread | raw e-mail | index | archive | help
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. > Thanks for all of the suggestions. I merged all of the suggestions and got a good result. What worked in the end was to upgrade to FreeBSD 8.1 and : * MAXPHYS is upped to be at least stripe_size * number_of_drives (and possibly 2x that, to use "fast mode" of gstripe) * vfs.hirunningspace is > MAXPHYS * the driver supports IOs of at least your stripe_size * the file system doesn't introduce unnecessary choppiness in IO (i.e. use soft-updates)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4CA48984.5030403>