Different buffered IO performance with SCSI and SATA with same unbuffered performance

[Pedro Larroy]

Hello. I'm puzzled about these measures with one U2W/160 SCSI disk and
a WD raptor SATA.
kernel is 2.6.28.7
This measures are on the same box, notice the very low rate of
buffered with the sata drive.

sata drive:
hdparm -t /dev/sdb
Timing buffered disk reads:   54 MB in  3.04 seconds =  17.78 MB/sec
hdparm --direct -t /dev/sdb
Timing O_DIRECT disk reads:  178 MB in  3.03 seconds =  58.67 MB/sec

scsi drive:
hdparm -t /dev/sda
Timing buffered disk reads:  200 MB in  3.03 seconds =  66.10 MB/sec
hdparm --direct -t /dev/sda
Timing O_DIRECT disk reads:  200 MB in  3.02 seconds =  66.14 MB/sec

Is this ok?

Regards. Pedro.

Attachment: config
Description: Binary data