Slow I/O with SMP, Fusion-MPT and u160 SCSI JBOD

Phil Dier
2005-09-14T20:01:14Z

Hi,

I just tried the 2.6.14-rc1 kernel to see if it exhibits the behaviour
I have described before[0]. It still does. Briefly, I have a dual Xeon
2.8 with 4GB ram, 1 adaptec and 1 fusion-mpt scsi device, each connected
to 1 SCSI JBOD with 5 disks apiece[1]. I/O on scsi ids 0 and 1 both
work flawlessly. I built an md device across ids 2 and 3, and the disks
connected to the fusion-mpt are unbearably slow. This behaviour was not
present in 2.6.12.3. When I partition the devices in question and mount
a filesystem on them, they exhibit the same behaviour individually.

[0]: http://www.ussg.iu.edu/hypermail/linux/kernel/0508.3/1233.html
[1]: http://www.icglink.com/debug-2.6.14-rc1.html

Here is what iostat looks like during what should be heavy I/O (my
tesh.sh script described in [1] is running), showing only the relevant
devices:

$ iostat 1 -k | awk '/(Device|md5|md6|md7)/{print $0;}'
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.62 0.00 2.46 244 198312
md6 0.62 0.00 2.46 228 198312
md7 0.61 0.01 2.45 440 197856
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 25.74 0.00 102.97 0 104
md6 25.74 0.00 102.97 0 104
md7 9.90 0.00 39.60 0 40
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 59.41 0.00 237.62 0 240
md6 60.40 3.96 237.62 4 240
md7 20.79 3.96 79.21 4 80
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 100.99 0.00 403.96 0 408
md6 100.99 0.00 403.96 0 408
md7 72.28 0.00 289.11 0 292
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 16242.57 0.00 64970.30 0 65620
md6 16242.57 0.00 64970.30 0 65620
md7 16230.69 0.00 64922.77 0 65572
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 1014.85 0.00 4059.41 0 4100
md6 1014.85 0.00 4059.41 0 4100
md7 1014.85 0.00 4059.41 0 4100
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 3298.02 0.00 13192.08 0 13324
md6 3298.02 0.00 13192.08 0 13324
md7 3298.02 0.00 13192.08 0 13324
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 2789.11 0.00 11156.44 0 11268
md6 2789.11 0.00 11156.44 0 11268
md7 2789.11 0.00 11156.44 0 11268
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
md5 0.00 0.00 0.00 0 0
md6 0.00 0.00 0.00 0 0
md7 0.00 0.00 0.00 0 0

Thanks for looking. Please cc me on replies.