Fri, Jun 06, 2003 at 03:40:45PM +1000, Nathan Scott wrote:
> > Some input/ideas/fixes would be appreciated.
>
> Oh - I wonder if the layering of RAID like this is causing the
> mkfs code to get confused. (is Martin lurking on the list?)
>
> I'd suggest trying a mkfs on one of the RAID5 devices, then pass
> those sunit and swidth values into mkfs rather than using the
> ones which it figures out on the fly from your RAID0 device, and
> see if that helps at all.
That wouldn't be advisable as the inner chunk size is only 32KB.
To get maximal performance from the raid it would need to write/read
2 x 256KB (512KB) to the outer raid for each I/O op. It would be nice
if the number of data disks in each raid5 was a power of two, but it
works out a write of 192KB would cover all 6 disks. 256KB or 128KB
is the closest approximation.
> > Btw, the filesystem was created using xfsprogs 2.0.6. After talking with
> > sandeen
> > he suggested that the newer utils had some changes relating to setting to
> > the sunit
> > and stripe perameters of the filesystem. Is this the case?
>
> There were changes recently in the MD stripe detection code, just
> to change it so that it wouldn't quit out of mkfs in certain cases
> and instead warn and carry on - so that wouldn't affect you here.
> It's a good idea to get the latest tools though - you might find
> version 2 logs to be of some help here too, and there was a recent
> mkfs fix for those recently.
Check out:
meta-data=/ isize=256 agcount=336, agsize=1048544 blks
= sectsz=512
data = bsize=4096 blocks=351630368, imaxpct=25
= sunit=32 swidth=64 blks, unwritten=1
naming =version 2 bsize=4096
log =internal bsize=4096 blocks=32768, version=1
= sectsz=512 sunit=0 blks
realtime =none extsz=262144 blocks=0, rtextents=0
What exactly is sunit? Is it meant to be the stripe chunk size for the given
device? If it is, then it should be 256, not 32. That could be the reason
for the shoddy performance?
Cheers
Patrick
--
Patrick Cole <Patrick.Cole@xxxxxxxxxx>
Programmer, the John Curtin School of Medical Research, ANU
Office 02 6125 6794 Mobile 0438 763337
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