Maxtor disks & DEC5000

[Mike Iglesias]

In article <768 at inesc.UUCP> pjd at inesc.UUCP (Paulo Jorge Delgado) writes:
>
>	We have installed the following configuration:
>
>DECstation 5000/200 (RISC)	- ULTRIX 4.0	- Maxtor XT-8380S
>
>DECstation 2100 (RISC)		- ULTRIX 4.0	- Maxtor LXT-200
>
>	The disks are rated at 14.5ms and 15ms typical seek time against 24ms
>for DEC's RZ55 disks, but I am getting very bad performance ratios for the
>Maxtor disks, using the DISKPERF benchmarks:
>
> [stuff deleted...]
>
>	I believe this bad performance of the Maxtor disks is due to the kernel
>not being able to use all the features of this disks. There is no entry in the
>Ultrix tables (/sys/data/scsi_data.c , /etc/disktab) for the Maxtor disks, so I
>had to install them as RZ55 devices.
>	I would like to know if there is any configuration procedure I could do
>(eg : recompiling the kernel with some changes), to improve the disks
>performance (I am mainly interested in improving the DEC 5000-Maxtor XT8380S
>pair performance).

You may need to turn on the readahead cache on the disk - we got some
Maxtor XT8380s drives that had it turned off.  You can do it with
the rzdisk program:

  # rzdisk -c ask /dev/rrz0a

Go down to page 8; it will ask you if you want to set the read cache disable
bit.  Answer "n".  Keep going until it asks you if you want to save
the info on the disk - answer "y".

You should read the man page for rzdisk before you attempt this.


Mike Iglesias
University of California, Irvine
Internet:    iglesias at draco.acs.uci.edu
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