FW: Poor performance, high disk queue on software RAID partition

Rechenberg, Andrew (arechenberg@shermfin.com)
Tue, 10 Dec 2002 08:08:32 -0500


I posted this issue to a couple of lists (linux-raid, redhat-list,
linux-poweredge) and have gotten a few responses, but none that really
point to a culprit. One of them suggested the issue may be
kernel-related so I'm forwarding this mail to the list.

If anyone can provide any assistance, I would be indebted.

Thanks,
Andy.

-----Original Message-----
From: Rechenberg, Andrew
Sent: Friday, December 06, 2002 5:08 PM
To: linux-poweredge@dell.com; 'redhat-list@redhat.com';
'linux-raid@vger.kernel.org'
Subject: Poor performance, high disk queue on software RAID partition

I have a Dell PowerEdge 6600, quad Xeon 1.4GHz, HT enabled, 8GB RAM,
with a PERC3/QC attached to two Dell PowerVault 220S disk SCSI disk
arrays. The PERC is doing hardware RAID1 across twenty-four 36GB 15K
SCSI disks (12 RAID1 arrays). Due to limitations with the PERC
firmware, I am running Linux software RAID0 across those 12 RAID1
arrays, effectively creating a RAID10 array. There is an ext3
filesystem on top of this md device (/dev/md0) in data=ordered mode.
The box is running a standard Red Hat 7.3 installation with updates, and
kernel 2.4.18-17.7.xbigmem

The database system running on this box is IBM (Ardent/Informix)
UniVerse. The application running on top of UniVerse accesses 25-30
large files (1-1.8GB) on a consistent basis. All ~400 users, plus any
batch processes, access these files, sometimes simultaneously (poor
application IMO).

Lately we've double the number of records in those database files and
now there seems to be some serious problems with disk I/O. The system
is hardly swapping at all, but the average disk queue and the average
wait time for I/O are both WAY out of wack. If I'm reading iostat
correctly some disks are waiting up to 6000ms for I/O!?!?! There is
nothing in 'top' that shows any process consuming more than about 60% of
one CPU.

Some stats from my box are provided below. The first iostat is since
the system booted. The second iostat is a sample from a 'iostat -x 1
10'

Is there any advice from the gurus out there as to where to turn next?
Would FiberChannel HBA's and drives help out any? Is there any
kernel/filesystem tuning I could perform to help out? If anyone needs
any information which I have forgotten, please let me know.

Thanks for your help,
Andy.

[root@mybox ~]# uname -a
Linux mybox.shermfin.com 2.4.18-17.7.xbigmem #1 SMP Tue Oct 8 12:07:59
EDT 2002 i686 unknown

[root@mybox ~]# free
total used free shared buffers
cached
Mem: 7483280 7471648 11632 0 52812
6957472
-/+ buffers/cache: 461364 7021916
Swap: 2048248 27916 2020332

[root@mybox ~]# cat /proc/sys/vm/bdflush
40 10 0 0 60 512 60 0 0

[root@mybox ~]# vmstat 1 10
procs memory swap io system
cpu
r b w swpd free buff cache si so bi bo in cs us
sy id
0 6 1 27448 12092 57000 6957196 0 0 0 3 11 14 10
10 1
0 6 1 27448 11896 57088 6958428 0 0 1504 12536 2026 712 2
7 91
0 6 1 27448 10668 56168 6959276 0 0 1112 13376 1806 562 2
4 94
0 6 0 27448 11892 56248 6958616 0 0 1260 8144 2076 761 2
3 96
0 6 1 27448 12352 56344 6958800 0 0 1792 12696 1977 897 2
5 93
0 6 1 27448 13268 56432 6958956 0 0 1608 12636 1992 676 2
7 91
1 6 1 27448 13316 56504 6959908 0 0 1216 9488 1922 528 2
5 93
0 6 0 27448 11568 55464 6960596 0 0 2532 12048 2234 1218 3
7 90
1 5 0 27448 12852 55552 6958104 0 0 1324 10620 2005 746 1
3 96
0 6 1 27448 11772 55632 6959992 0 0 2504 14000 2004 1032 3
9 87

[root@mybox ~]# iostat -x
Linux 2.4.18-17.7.xbigmem (mybox.shermfin.com) 12/06/2002

avg-cpu: %user %nice %sys %idle
9.31 0.66 9.94 80.09

Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s
avgrq-sz avgqu-sz await svctm %util
/dev/sda 2.25 17.49 1.66 19.56 28.36 297.10 14.18 148.55
15.33 0.22 12.52 6.23 1.32
/dev/sda1 0.34 0.00 0.03 0.00 0.72 0.01 0.36 0.00
27.66 0.00 54.88 9.87 0.00
/dev/sda5 0.04 7.29 0.03 5.28 0.49 101.71 0.25 50.86
19.25 0.15 13.13 32.48 1.72
/dev/sda6 1.54 1.64 1.11 2.55 20.86 33.18 10.43 16.59
14.76 0.00 35.58 25.23 0.92
/dev/sda7 0.18 2.48 0.20 5.55 2.66 63.92 1.33 31.96
11.57 0.02 23.66 35.51 2.04
/dev/sda8 0.00 0.21 0.12 0.02 0.93 1.82 0.46 0.91
20.36 0.03 227.99 22.47 0.03
/dev/sda9 0.15 5.87 0.18 6.16 2.69 96.46 1.35 48.23
15.64 0.03 22.68 20.08 1.27
/dev/sdb 107.30 343.83 11.74 20.33 952.36 2919.18 476.18 1459.59
120.72 0.09 4.71 5.89 1.89
/dev/sdb1 107.30 343.83 11.74 20.33 952.36 2919.18 476.18 1459.59
120.72 0.24 4.71 3.86 1.24
/dev/sdc 47.55 68.38 36.92 84.22 675.77 1224.12 337.88 612.06
15.68 0.10 2.92 1.39 1.69
/dev/sdc1 47.55 68.38 36.92 84.22 675.77 1224.12 337.88 612.06
15.68 0.09 2.92 0.61 0.74
/dev/sdd 47.56 71.20 37.02 73.78 676.68 1169.03 338.34 584.52
16.66 0.03 1.96 2.12 2.35
/dev/sdd1 47.56 71.20 37.02 73.78 676.68 1169.03 338.34 584.52
16.66 0.07 1.96 0.05 0.06
/dev/sde 47.57 70.71 36.86 64.76 675.44 1092.64 337.72 546.32
17.40 0.04 4.05 1.99 2.03
/dev/sde1 47.57 70.71 36.86 64.76 675.44 1092.64 337.72 546.32
17.40 0.24 4.05 1.33 1.35
/dev/sdf 47.54 68.05 36.78 64.35 674.59 1066.89 337.30 533.44
17.22 0.15 0.74 1.38 1.40
/dev/sdf1 47.54 68.05 36.78 64.35 674.59 1066.89 337.30 533.44
17.22 0.14 0.74 2.02 2.04
/dev/sdg 47.53 72.40 36.87 65.03 675.21 1112.15 337.60 556.08
17.54 0.05 2.28 1.67 1.70
/dev/sdg1 47.53 72.40 36.87 65.03 675.21 1112.15 337.60 556.08
17.54 0.04 2.28 0.97 0.98
/dev/sdh 47.51 69.04 36.95 71.88 675.75 1137.24 337.88 568.62
16.66 0.10 4.27 0.55 0.60
/dev/sdh1 47.51 69.04 36.95 71.88 675.75 1137.24 337.88 568.62
16.66 0.13 4.27 0.26 0.29
/dev/sdi 47.55 70.55 36.81 66.15 674.85 1105.14 337.42 552.57
17.29 0.15 3.24 2.26 2.33
/dev/sdi1 47.55 70.55 36.81 66.15 674.85 1105.14 337.42 552.57
17.29 0.07 3.24 1.86 1.92
/dev/sdj 47.54 71.97 36.82 72.62 674.89 1161.19 337.44 580.60
16.78 0.04 1.26 2.09 2.29
/dev/sdj1 47.54 71.97 36.82 72.62 674.89 1161.19 337.44 580.60
16.78 0.07 1.26 1.15 1.26
/dev/sdk 47.55 66.96 36.92 72.86 675.80 1125.62 337.90 562.81
16.41 0.12 0.14 2.05 2.25
/dev/sdk1 47.55 66.96 36.92 72.86 675.80 1125.62 337.90 562.81
16.41 0.21 0.14 1.91 2.10
/dev/sdl 47.55 66.37 36.98 61.95 676.19 1038.09 338.09 519.05
17.33 0.19 3.08 1.31 1.29
/dev/sdl1 47.55 66.37 36.98 61.95 676.19 1038.09 338.09 519.05
17.33 0.14 3.08 0.57 0.56
/dev/sdm 47.58 68.40 36.83 79.35 675.24 1189.25 337.62 594.62
16.05 0.14 1.84 1.17 1.36
/dev/sdm1 47.58 68.40 36.83 79.35 675.24 1189.25 337.62 594.62
16.05 0.16 1.84 1.55 1.80
/dev/sdn 47.58 72.05 36.80 92.70 675.04 1321.50 337.52 660.75
15.42 0.11 3.38 1.25 1.63
/dev/sdn1 47.58 72.05 36.80 92.70 675.04 1321.50 337.52 660.75
15.42 0.13 3.38 0.39 0.50
/dev/sdo 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
8.00 0.00 150.00 150.00 0.00

avg-cpu: %user %nice %sys %idle
1.75 0.00 5.12 93.12

Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s
avgrq-sz avgqu-sz await svctm %util
/dev/sda 0.00 2.00 0.00 6.00 0.00 64.00 0.00 32.00
10.67 42948592.96 0.00 1666.67 100.00
/dev/sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
/dev/sda5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 20.00 0.00 0.00 100.00
/dev/sda6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 42949612.96 0.00 0.00 100.00
/dev/sda7 0.00 1.00 0.00 3.00 0.00 32.00 0.00 16.00
10.67 42949662.96 0.00 3333.33 100.00
/dev/sda8 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
/dev/sda9 0.00 1.00 0.00 3.00 0.00 32.00 0.00 16.00
10.67 42949662.96 0.00 3333.33 100.00
/dev/sdb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 42949642.96 0.00 0.00 100.00
/dev/sdb1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 42949662.96 0.00 0.00 100.00
/dev/sdc 7.00 164.00 13.00 55.00 160.00 2152.00 80.00 1076.00
34.00 458.34 328.24 147.06 100.00
/dev/sdc1 7.00 164.00 13.00 55.00 160.00 2152.00 80.00 1076.00
34.00 288.34 328.38 147.06 100.00
/dev/sdd 15.00 162.00 20.00 103.00 288.00 2288.00 144.00 1144.00
20.94 42949518.02 1212.11 81.30 100.00
/dev/sdd1 15.00 162.00 20.00 103.00 288.00 2288.00 144.00 1144.00
20.94 325.06 1212.11 81.30 100.00
/dev/sde 11.00 143.00 18.00 103.00 232.00 2112.00 116.00 1056.00
19.37 347.64 1612.81 82.64 100.00
/dev/sde1 11.00 143.00 18.00 103.00 232.00 2112.00 116.00 1056.00
19.37 147.64 1612.89 70.25 85.00
/dev/sdf 13.00 164.00 30.00 126.00 328.00 2440.00 164.00 1220.00
17.74 42949618.47 1045.06 63.85 99.60
/dev/sdf1 13.00 164.00 30.00 126.00 328.00 2440.00 164.00 1220.00
17.74 315.51 1045.06 64.10 100.00
/dev/sdg 6.00 190.00 22.00 62.00 224.00 2560.00 112.00 1280.00
33.14 455.15 840.83 119.05 100.00
/dev/sdg1 6.00 190.00 22.00 62.00 224.00 2560.00 112.00 1280.00
33.14 215.15 840.71 119.05 100.00
/dev/sdh 12.00 161.00 18.00 62.00 240.00 2312.00 120.00 1156.00
31.90 42949587.08 641.62 124.50 99.60
/dev/sdh1 12.00 161.00 18.00 62.00 240.00 2312.00 120.00 1156.00
31.90 42949567.08 641.50 125.00 100.00
/dev/sdi 7.00 167.00 16.00 100.00 176.00 2328.00 88.00 1164.00
21.59 541.66 2272.07 86.21 100.00
/dev/sdi1 7.00 167.00 16.00 100.00 176.00 2328.00 88.00 1164.00
21.59 91.66 2272.16 84.91 98.50
/dev/sdj 5.00 168.00 14.00 59.00 160.00 2256.00 80.00 1128.00
33.10 108.94 1263.97 125.75 91.80
/dev/sdj1 5.00 168.00 14.00 59.00 160.00 2256.00 80.00 1128.00
33.10 58.94 1263.97 136.44 99.60
/dev/sdk 16.00 147.00 22.00 80.00 312.00 2144.00 156.00 1072.00
24.08 500.53 1574.12 98.04 100.00
/dev/sdk1 16.00 147.00 22.00 80.00 312.00 2144.00 156.00 1072.00
24.08 370.53 1574.22 98.04 100.00
/dev/sdl 5.00 146.00 15.00 96.00 152.00 2032.00 76.00 1016.00
19.68 42949660.85 2192.25 83.42 92.60
/dev/sdl1 5.00 146.00 15.00 96.00 152.00 2032.00 76.00 1016.00
19.68 477.89 2192.16 90.09 100.00
/dev/sdm 15.00 146.00 20.00 125.00 280.00 2216.00 140.00 1108.00
17.21 977.33 2383.52 68.97 100.00
/dev/sdm1 15.00 146.00 20.00 125.00 280.00 2216.00 140.00 1108.00
17.21 347.33 2383.52 68.97 100.00
/dev/sdn 9.00 166.00 13.00 79.00 184.00 2344.00 92.00 1172.00
27.48 42949470.99 1155.00 108.70 100.00
/dev/sdn1 9.00 166.00 13.00 79.00 184.00 2344.00 92.00 1172.00
27.48 178.03 1155.11 108.70 100.00
/dev/sdo 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00

Andrew Rechenberg
Infrastructure Team, Sherman Financial Group
arechenberg@shermanfinancialgroup.com
Phone: 513.707.3809
Fax: 513.707.3838
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