IBM TS2340 User Guide - Page 70
Common AIX Utilities, AIX iostat Utility for Tape Performance, Before Calling Support, iostat
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AIX Device Driver (Atape) Figure 8. Data Path for AIX Device Driver (Atape) Common AIX Utilities The most commonly reported cause for poor tape performance is the use of small block sizes or the modification of the installation defaults for the tape device. Note: The device parameters should not be changed from the defaults for most applications. The following guidelines typically result in good tape path performance for use with AIX utilities: 1. Hardware compression should be enabled for maximum performance if the data sent to the device is uncompressed. 2. The block_size parameter should be set to variable (block_size=0) and command or application parameters specified to a block size appropriate for the device. 3. Block sizes of 128 KB or greater should be used to improve performance. AIX iostat Utility for Tape Performance In releases of AIX 5.3 and earlier, the AIX iostat utility supports tape performance statistics in addition to other supported devices (such as disk). To determine if the iostat utility supports the configured tape drives, run the command iostat -p. If the configured tape drives are supported, a list of configured tape drives are displayed with the statistics listed for each drive. Refer to the AIX iostat man page for a complete description of the iostat command and parameters. When using the Data Path Failover feature, only the primary path for the tape drive is listed. The statistics apply to both the primary and alternate paths that are used. Before Calling Support System performance tuning is not a support responsibility. If tests indicate raw tape performance is below specifications, record the exact failing command and collect the output from the commands in Table 8 before contacting support. Table 8. Error Description Information Configuration Device parameters Error log. Call hardware support if errors are found for TAPE_ERR* or SCSI* error labels. Driver version Command lscfg -v lsattr -E -l rmtN errpt -a lslpp -l Atape.driver 52 IBM Tape Device Drivers Installation and User's Guide