SCSI adaptec 19160 speed - 2.6.14-rt13 - Q for scsi experts

[art]

SCSI adaptec 19160 speed - 2.6.14-rt13 - Q for scsi experts

Attached scsi disk sda at scsi0, channel 0, id 1, lun 0
  Vendor: COMPAQ    Model: BF14688286        Rev: HPB3
  Type:   Direct-Access                      ANSI SCSI revision: 03
scsi0:A:2:0: Tagged Queuing enabled.  Depth 64
target0:0:2: Beginning Domain Validation
target0:0:2: wide asynchronous.
target0:0:2: FAST-80 WIDE SCSI 160.0 MB/s DT (12.5 ns, offset 63)
target0:0:2: Ending Domain Validation
SCSI device sdb: 286749488 512-byte hdwr sectors (146816 MB)
SCSI device sdb: drive cache: write through
SCSI device sdb: 286749488 512-byte hdwr sectors (146816 MB)
SCSI device sdb: drive cache: write through
sdb: sdb1
Attached scsi disk sdb at scsi0, channel 0, id 2, lun 0
  Vendor: COMPAQ    Model: BF14688286        Rev: HPB3
  Type:   Direct-Access                      ANSI SCSI revision: 03
scsi0:A:5:0: Tagged Queuing enabled.  Depth 64
target0:0:5: Beginning Domain Validation
target0:0:5: wide asynchronous.
target0:0:5: FAST-80 WIDE SCSI 160.0 MB/s DT (12.5 ns, offset 63)
target0:0:5: Ending Domain Validation
SCSI device sdc: 286749488 512-byte hdwr sectors (146816 MB)
SCSI device sdc: drive cache: write through
SCSI device sdc: 286749488 512-byte hdwr sectors (146816 MB)
SCSI device sdc: drive cache: write through
sdc: sdc1
Attached scsi disk sdc at scsi0, channel 0, id 5, lun 0

# hdparm -tT /dev/sdb
/dev/sdb:
Timing cached reads:   2316 MB in  2.00 seconds = 1157.90 MB/sec
Timing buffered disk reads:  268 MB in  3.00 seconds =  89.26 MB/sec
# hdparm -tT /dev/sdc

/dev/sdc:
Timing cached reads:   2512 MB in  2.00 seconds = 1255.49 MB/sec
Timing buffered disk reads:  268 MB in  3.00 seconds =  89.32 MB/sec

# hdparm -tT /dev/sdb & hdparm -tT /dev/sdc &
[1] 3314
[2] 3315

/dev/sdb:
/dev/sdc:
Timing cached reads:    Timing cached reads:   1228 MB in  2.00 seconds = 613.88 MB/sec
1316 MB in  1.99 seconds = 659.73 MB/sec
Timing buffered disk reads:   Timing buffered disk reads:
174 MB in  3.00 seconds =  57.91 MB/sec
170 MB in  3.05 seconds =  55.75 MB/sec
------------------------------------------------------------------------------------------

pci is 66Mhz theoretical throuhput ~ 250MB/s

controller adaptec asc-19160
discs are 146GB-15krpm-cheetah

one disc transfer 89MB/s

adaptec speed with 2 disc on one channel = 57.91+55.75 = 113.66MB/s

71% of 160MB/s channel speed i expected ~90%

any clue?

xboom
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