how do i efficiently read an ntbackup tape

[paul broadway]

I have been sent a large file that has been written to a DLT tape on an NT server using 'ntbackup'.
Using default settings on the 'dd' command, this tape is taking an age to process (for the 8GB file it will take about 32 hours!!).
Has anyone got any ideas on the best way to read this tape?

[James R. Ferguson · Accepted solution]

Hi:

Try increasing the block size. The default is only 512-characters. You might use 'bs=100b' for example to utilize a 51200-character block. See 'man dd' for all options.

...JRF...

[Magdi KAMAL]

Hi Nigel,

I agree with James for the block size. But if you could give a number which is a multiplication factor to enhance the the association between physical and logical blocks , this could be really better.
Example :
1. Physical block is 512 k.
2. One logical read is 32 physical blocks.
3. So, you block size must be 16 MB in order that what you get in only one I/O is transfered to tape.

Highlight the lampe on the DLT drive so compression and high density are used.

I'm using HP OpenView OmniBack II and DLT 8000 to save huge file-systems and I reached a rate of 28 GB/hour ( with the streaming mode : that's means that the files are big enough to speed the write process on the tape and no tape rewind is made ).