Slow SCSI under linux-2.1.123-2.aic-pre10

[Rune Frøysa]

SCSI is slow under linux on a Dell Precision 410. /dev/sdb is a 6*9Gb
Raid0 set (connected to the scsi port on the back), which
theoretically should get somehing like 30-40MB/s. I get 9.61, which is
slower than the local disk.

scsi0 : Adaptec AHA274x/284x/294x (EISA/VLB/PCI-Fast SCSI) 5.1.0pre10/3.2.4
       <Adaptec AIC-7890/1 Ultra2 SCSI host adapter>
scsi1 : Adaptec AHA274x/284x/294x (EISA/VLB/PCI-Fast SCSI) 5.1.0pre10/3.2.4
       <Adaptec AIC-7880 Ultra SCSI host adapter>
scsi : 2 hosts.
  Vendor: QUANTUM   Model: VIKING II 9.1WLS  Rev: 3506
  Type:   Direct-Access                      ANSI SCSI revision: 02
Detected scsi disk sda at scsi0, channel 0, id 0, lun 0
(scsi0:0:0:0) Synchronous at 80.0 Mbyte/sec, offset 31.
  Vendor: CRD-5330  Model: UR53-600S         Rev: C1-2
  Type:   Direct-Access                      ANSI SCSI revision: 02
Detected scsi disk sdb at scsi1, channel 0, id 0, lun 0
(scsi1:0:0:0) Synchronous at 40.0 Mbyte/sec, offset 8.

/local/oracle at myrddraal #hdparm -t /dev/sda

/dev/sda:
 Timing buffered disk reads:  32 MB in  2.55 seconds =12.55 MB/sec

/local/oracle at myrddraal #hdparm -t /dev/sdb

/dev/sdb:
 Timing buffered disk reads:  32 MB in  3.33 seconds = 9.61 MB/sec

Also, Linux started swapping a lot during mke2fs on the 54GB filesystem,
using > 120MB memory for buffers (I have 128).

-- 
Rune Frøysa                            Private e-mail: runefr at ifi.uio.no
UNIX evangelist
"Where do your encryption keys want to go today?" - Peter Gutmann

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