[5170] in linux-scsi channel archive
aic7xxx driver 5.1.4 slower than 5.1.2?
daemon@ATHENA.MIT.EDU (Venkatesh Krishnamurthi)
Thu Nov 19 03:59:24 1998
From: vk@spies.com (Venkatesh Krishnamurthi)
To: linux-scsi@vger.rutgers.edu
Date: Wed, 18 Nov 1998 09:09:09 -0800 (PST)
The 5.1.4 version of the aic7xxx driver in kernel 2.0.36 (and kernel
2.1.128) causes the drives to return lower values with hdparm.
On my system (2 x PII 350 Mhz on a ASUS-P2BDS with 2 IBM 9ZX UW drives):
Combination hdparm -tT /dev/sda values:
----------- --------------------------
5.1.2 / kernel 2.0.35 16.16 MB/sec
5.1.4 / kernel 2.0.36 14.45 MB/sec
5.1.4 / kernel 2.1.128 14.45 MB/sec
Also the 5.1.2 driver identified the drive as:
Vendor: IBM Model: DGVS09U Rev: 0
Type: Direct-Access ANSI SCSI revision: 03
Detected scsi disk sda at scsi0, channel 0, id 0, lun 0
(scsi0:0:0:0) Synchronous at 40.0 Mbyte/sec, offset 15
while the 5.1.4 driver reports:
Vendor: IBM Model: DGVS09U Rev: 0
Direct-Access ANSI SCSI revision: 03
Detected scsi disk sda at scsi0, channel 0, id 0, lun 0
(scsi0:0:0:0) Synchronous at 20.0 Mbyte/sec, offset 15
i.e. the interface speed is correctly shown as 40 Mbyte/sec in 5.1.2 while
it shows up as 20 Mbyte/sec in 5.1.4.
My experiments with copying files across the two drives showed a slight
slowdown with the 5.1.4 driver. The difference was small enough (~4%) to have
been within the range of experimental errors.
A Mylex Flashpoint LW adapter returned 16.16 MByte/sec on the hdparm test
and also reported the drive interface speed as 40 MByte/sec.
Venkatesh
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