Re: raid 10 su, sw settings

Justin Piszcz
2007-12-31T17:04:45Z

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On Sun, 30 Dec 2007, Brad Langhorst wrote:

> I have this system
> - 3ware 9650 controller
> - 4 disk raid 10
> - 64k stripe size
> - this is a vmware host, so lots of r/w on a few big files.
>
> I'm not entirely satisfied with its performance.
>
> Typical blocks/sec from iostat during large file movements is about
> 100M/s read and 80M/s write.
>
> When I set this up, I did not fully understand all the details... so I
> want to check a few things.
>
> - is the partition aligned correctly? i fear not...
> /dev/sda1 * 1 24 192748+ 83 Linux
> /dev/sda2 25 19449 156031312+ 83 Linux
>
> Is this where I'm losing performance?
>
> - What should the sunit and swidth settings be during mount?
> I guess with raid 10 the width is 2 so...
> sunit = 128 (64k/512) and swidth = 256 (2*64k/512)
>
> Or maybe I should use width 1 ?
> ÿÿ
> Remounting (mount -o remount) with these options does not lead
> to a noticeable change in performance. Must I recreate the fs or
> unmount and remount?
>
> Here's the output of xfsinfo in case it's relevant.
>
> xfs_info /
> meta-data=/dev/sda2 isize=256 agcount=16, agsize=2437989
> blks
> = sectsz=512 attr=0
> data = bsize=4096 blocks=39007824,
> imaxpct=25
> = sunit=0 swidth=0 blks, unwritten=1
> naming =version 2 bsize=4096
> log =internal bsize=4096 blocks=19046, version=1
> = sectsz=512 sunit=0 blks
> realtime =none extsz=65536 blocks=0, rtextents=0
>
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#1 What type of performance do you expect with a 4-disk raid10?
#2 You should be able to umount/mount with the new sizes, although I have
not tested it myself b/c I typically use sw raid here (sunit/etc is
optimized for sw raid).

Justin.