A5200 front disks extremely slow

keller.jack_at_jdirving.com
Date: 03/23/05 

Date: 23 Mar 2005 13:37:05 -0800

I have a problem with an A5200. All the front disks are performing
extremely poorly. The rear drives seem normal. There are no errors
being reported and all the disks are the same make and model with
the same firmware:

        Vendor: SEAGATE Product: ST336704FSUN36G Revision: 1526

To illustrate, here's the output of a newfs and iostat of one of the
front drives:

time echo 'y' | newfs /dev/rdsk/c0t42d0s7
Warning: cylinder groups must have a multiple of 16 cylinders with the
given
         parameters
Rounded cgsize up to 256
Warning: 1 sector(s) in last cylinder unallocated
/dev/rdsk/c0t42d0s7: 71112734 sectors in 24615 cylinders of 27
tracks, 107 sectors
        34723.0MB in 770 cyl groups (32 c/g, 45.14MB/g, 5632 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
 32, 92592, 185152, 277712, 370272, 462832, 555392, 647952, 740512,
833072,
Initializing cylinder groups:
...............
super-block backups for last 10 cylinder groups at:
 70263200, 70355760, 70448320, 70540880, 70633440, 70726000, 70818560,
 70911120, 71000096, 71092656,

real 4m25.65s
user 0m3.79s
sys 0m0.43s

                    extended device statistics
    r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
    0.0 5.0 0.0 1849.6 6.1 15.0 1221.9 2999.9 100 100 c0t42d0
                    extended device statistics
    r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
    0.0 5.0 0.0 1780.0 6.6 15.0 1315.8 3000.0 100 100 c0t42d0
                    extended device statistics
    r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
    0.0 6.8 0.0 2420.8 5.1 15.0 744.5 2202.2 90 100 c0t42d0
                    extended device statistics
    r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
    0.0 7.0 0.0 2422.4 6.4 15.0 908.8 2142.8 100 100 c0t42d0
                    extended device statistics
    r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
    0.0 6.8 0.0 2420.8 5.2 15.0 762.7 2205.9 100 100 c0t42d0

The output from the same operation on one of the rear drives:

time echo 'y' | newfs /dev/rdsk/c0t58d0s7

Warning: cylinder groups must have a multiple of 16 cylinders with the
given
         parameters
Rounded cgsize up to 256
Warning: 1 sector(s) in last cylinder unallocated
/dev/rdsk/c0t58d0s7: 71112734 sectors in 24615 cylinders of 27
tracks, 107 sectors
        34723.0MB in 770 cyl groups (32 c/g, 45.14MB/g, 5632 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
 32, 92592, 185152, 277712, 370272, 462832, 555392, 647952, 740512,
833072,
Initializing cylinder groups:
...............
super-block backups for last 10 cylinder groups at:
 70263200, 70355760, 70448320, 70540880, 70633440, 70726000, 70818560,
 70911120, 71000096, 71092656,

real 0m26.61s
user 0m4.10s
sys 0m0.41s

                    extended device statistics
    r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
    2.6 54.6 1.5 19082.3 2.8 10.7 49.2 187.6 64 73 c0t58d0
                    extended device statistics
    r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
    0.0 71.4 0.0 25279.7 5.7 15.0 80.3 210.0 100 100 c0t58d0
                    extended device statistics
    r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
    1.2 107.4 6.5 11087.7 109.6 13.2 1009.6 121.3 82 91 c0t58d0

Elapsed time for the front drive is 10 times that of the rear
drive. The iostat output shows extremely high service times for
the front drive. What could be causing that?

TIA
Jack