The Question is:
I have a DS20E with a TZ-88, I also have an Alpha1000 with a DLT4000, both
running V7.3. The backups are fairly fast 110 QI/O's, however, the restores
take 4 times as long, and the QI/O's barely get above 30. I've had VAX's at
other sites push similar d
rives nearly 10 times faster.
These are newly installed systems. What parameters should I set to get these
tape drives running at their "Peak" performance, especially on "reads" ?????
The Answer is :
The performance of BACKUP has been measured to be within 90% of the
slowest hardware component between the source and the target, with
proper system parameter and process quota settings.
For the recommended settings for the BACKUP operator, please see the
system manager's manual in the OpenVMS documentation. Also please
see the performance management manual.
For system parameter settings, please see AUTOGEN documentation;
please use AUTOGEN with FEEDBACK to adjust the system parameters.
In the OpenVMS performance management documentation, please see the
details on locating and resolving I/O performance limits. (In this
particular case, check for deepening I/O queues on the target disk
device -- an average deeper than 0.5 pending disk I/O operations
would indicate half of all I/O requests are stalling. This value
can be easily monitored with MONITOR DISK/ITEM=QUEUE_LENGTH.)
Please contact the support center for additional assistance, as the
details of the two I/O subsystems involved here will be required.