Slow Tape Drive speed has been observed daily that is causing the Staging Images created using DSSU Staging policy to have much longer time to copy to the Tapes. Tape Drive speed only varies between 5-10 MB/sec that is below par of the normal Tape Drive Speed. I have tried to find out the tuning parameters and have applied the following changes to the following parameters:
SIZE_DATA_BUFFERS: 262144 (256k)
Still no better changes have been observed due to above tuning parameters.
The Tape Drive Details being used are of type HCART3. There are two Tape Drives being used that are HP.ULTRIUM.SCSI. The Tape Library used is C4 Tape Library.
The Netbackup version is 6.0 MP5.
Please let me know if there is any further information any one requires for understanding the problem.
Check the bpkar output ..... if the throughput of bpkar and actual backup job differs immensly..... there is an issue with the hardware or connectivity.......
Have the bpkar values in hand to getter a better picture.
Are you running backup while staging ?. Writing and reading give very bad transfer performance.
What's the disk/array capacity, have you verified the array can handle >80MB/sec. Try using vxbench,Bonnie++ or alike.
Bad tape drive, seen this before - If the tape drive is close to be worn out, it will perform multiple re-write because the read after write failed. If more drive are limited to 10-15MB/sec, I don't think this is you're issue.