Date: Tue, 28 Sep 2010 12:44:44 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-performance@freebsd.org Subject: Re: gstripe small transaction size Message-ID: <i7sguk$gi2$1@dough.gmane.org> In-Reply-To: <4CA14009.4050906@softhammer.net> References: <4CA14009.4050906@softhammer.net>
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On 09/28/10 03:08, 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 ? > > gstripe label -v -s 131072 roadkill /dev/da0 /dev/da2 No pratical way. You have a gstripe array of two drives and with MAXPHYS of 128 KiB each would in fact see at most 64 KiB transactions. It gets worse when you add drives. > newfs /dev/stripe/roadkill Depending on what you are doing, adding "-U" would help you here.
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