HP OpenVMS Systems

ask the wizard
Content starts here

Determining disk I/O performance?

» close window

The Question is:

I need to copy 5M block files from one disk to another.
FTP,Copy or Backup can be used, but I would like to improve the
performance we are currently getting (1.5 hours on UW SCSI drives)
Any thoughts or papers on how to tune any of the above?

The Answer is :

  These files are apparently 2,560,000,000 bytes in size, circa 2.5 GB.
  Assuming a total transfer time of 5400 seconds, this storage transfer
  works out to a transfer rate of just under a half megabyte per second.
  For purposes of comparison, the specified transfer rates for the wide
  Ultra2 and Ultra3 disks range from 80 to 160 megabytes per second.
  That the disks involved are UltraSCSI is interesting.  That the remainder
  of the system environment (including hardware and software) can sustain
  UltraSCSI transfer rates would also be interesting information.
  Some guesses: the OpenVMS Wizard would assume that the disk spindles or
  the SCSI bus(es) are overloaded, that the system or SCSI is overloaded
  (or underconfigured), or that your system parameters and your process
  quotas are set to values that are insufficient, or that the tools used
  are insufficiently capable of maintaining the required transfer rate.
  This could also obviously be a problem with the UltraSCSI configuration,
  or with the particular UltraSCSI disk device(s) and controllers involved.
  For additional assistance in determining the factor(s) limiting your disk
  I/O performance, please contact your hardware support organization, or
  directly contact the folks at the Compaq Customer Support Center.  Expect
  to be asked details of your configuration and quotas, among other questions.

answer written or last revised on ( 9-JUL-2000 )

» close window