Steve,
Here is the output from xfs_info, please excuse the formatting. I am using
a chunk size of 4K in the raid. Larger sizes seem to degrade performance.
Thanks for your help.
With 14 disks in the array:
meta-data=/test isize=256 agcount=240, agsize=1048576
blks
data = bsize=4096 blocks=251392736,
imaxpct=25
= sunit=1 swidth=14 blks,
unwritten=1
naming =version 2 bsize=4096
log =external bsize=4096 blocks=32768 version=1
= sunit=0 blks
realtime =none extsz=57344 blocks=0, rtextents=0
With 15 disks in the array
meta-data=/test isize=256 agcount=257, agsize=1048576
blks
data = bsize=4096 blocks=269349360,
imaxpct=25
= sunit=1 swidth=15 blks,
unwritten=1
naming =version 2 bsize=4096
log =external bsize=4096 blocks=32768 version=1
= sunit=0 blks
realtime =none extsz=61440 blocks=0, rtextents=0
From: Steve Lord <lord@xxxxxxx>
To: Rick Smith <rgsmith72@xxxxxxxxxxx>
CC: linux-xfs@xxxxxxxxxxx
Subject: Re: U320 Large Array Performance
Date: 04 Feb 2003 16:16:05 -0600
On Tue, 2003-02-04 at 16:09, Rick Smith wrote:
> I am constructing a large, high performance U320 raid0 array with
XFS
> using the 2.4.20-rc1-xfs kernel and linux software raid. I am pleased
with
> the performance, but it seems that when I exceed 14 disks total in the
> single raid0 array, performance becomes erratic. With 14 disks and
under,
> the extents are laid out nicely in incrementing order very close to each
> other (according to xfs_bmap) and I can get very large MB/s numbers
using 4
> U320 SCSI channels and 73GB disks. However, with 15+ disks, I am seeing
> large, erratic gaps in the extents, which is seriously affecting
read/write
> performance. I don't exceed 5 drives per channel, and the problem seems
to
> exist no matter what SCSI configuration that I use. I have tried various
> numbers of channels and disks per channel, but the problem remains when
I
> exceed 14 disks. Currently the read performance for 15 disks is about
half
> the read performance for 14 disks in the array.
> Other filesystems tested (reiserfs and ext2/3) do not seem to suffer
> from this problem, but they also don't produce the awesome speed that
the
> XFS filesystem does.
> I plan on experimenting with the latest 2.4 and 2.5 versions of the
XFS
> kernel as soon as I can get a good copy from CVS.
> Any help is appreciated. Thanks.
Sounds like you need to play with mkfs options on XFS. Can you send
the output of xfs_info /mnt where /mnt is the mounted filesystem.
Steve
--
Steve Lord voice: +1-651-683-3511
Principal Engineer, Filesystem Software email: lord@xxxxxxx
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