9840 tape drive only has capacity of 10gb, how can i make it 20gb?

[lnbnatera]

hi,

i just noticed that the 9840 tape that we were using was just 10gb (mminfo -am). i confirmed the size of the tapes with the vendor and it should be 20gb.

i tried changing the volume default capacity in the devices section and tried to label one volume and the mminfo reported a 20gb capacity; however, instead of me getting around 40gb of data on tape, i still got 20bgb worth of exactly the same data. the device path is /dev/rmt/0cbn and the directive is unix with compression directives.

is there a way for me to fully maximize the tape drive? from what i can see we hare unable to use 50% of the expected capacity of the tape.

 

[GunnarD]

40GB is with compressed data (20GB uncompressed) but when you use "unix with compression" the data is already compressed when it comes to the server so you only get 20GB.

 

[605]

The volume default capacity is NOT a parameter that afffects capacity at all - it is only used as the reference to calculate the &used value for the media. Nice idea to use it to increase the true capacity - Legato should be awarded if this would be a true feature ;-)

If it does not encounter a hard error, NW will always write to the physical end-of-tape.

I also think that you should avoid to use compressasm. It could be that it harms more than anything else.

 

[lnbnatera]

605: I also think that you should avoid to use compressasm. It could be that it harms more than anything else.


what problems do compressasm bring?

 

[605]

Nobody really knows as at least the hardware compression is unknown. However, you simply should avoid to cascade multiple compression steps. I have heard that at least files can even become larger.