gstripe small transaction size

Stephen Sanders ssanders at
Tue Sep 28 12:45:10 UTC 2010

  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.


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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