SAM br_backup / fbackup and DDS drives

[winkel]

Which are the least tape-space and time-consuming parameters in fbackup_config when using a DDS-3 tape drive ?

I have a DDS-3 tape-drive; fbackup man pages recommend 64 as blocksperrecord for DDS-drives, but I think for DDS-2 DDS-3 and DDS-4 higher values will work as well and more efficient in time and tape-space; Currently I use this fbackup_config :
blocksperrecord 256 # default = 16
records 128 # default = 32
checkpointfreq 128 # default = 32
readerprocesses 2 # default
maxretries 2 # default = 5
retrylimit 5000000 # default
maxvoluses 500 # default = 100
filesperfsm 200 # default

[James R. Ferguson]

Hi:

A thread with many document references and some practial metrics is:

http://my1.itrc.hp.com/cm/QuestionAnswer/1,1150,0x4a4849c5ae73d4118fef0090279cd0f9,00.html

As you will see, 'blocksperrecord' parameter has generally been shown to have the biggest impact, along with readerproceses. Also, using /dev/rmt/Xm files normally gives the best compression the device supports.

...JRF...

[James R. Ferguson]

Hi:

BTW, a maximum of 500 uses for the tape seems a bit high. I prefer to stay with the default 100. I use maxretries=3 but otherwise my parameters are the same as yours.

...JRF...