I have an external DLT tape (a COMPAQ DLT VS 40/80 5133 according to camcontrol). It seems glacially slow to me. Last night I backed up many gigabytes of files from a remote machine over NFS. It took over five hours to do it. My overworked Sun E-450 will do this in a shade over three hours.
What is more, the remote machine and my FreeBSD box have gigabit Ethernet adapters, and both machines, as well as the switch they are connected to all report 1000baseT full duplex. The sun, on the other hand, is running 100baseT.
When I run a "tar t" to list the contents of the archive, the output is really slow. It's taken about half an hour so far to list the first 50 or so files (and none are exceptionally big, 10Mb on average).
When I listen to the tape drive, I hear it start and stop frequently, with lots of pauses. I would have expected it to spin continuously. It is, after all, a *streaming* device.
All of which makes me think that something is going unspecified somewhere. Something like a preferred block size?
'mt stat' produces the following:
Mode Density Blocksize bpi Compression Current: 0x40 variable 0 IDRC ---------available modes--------- 0: 0x40 variable 0 IDRC 1: 0x40 variable 0 IDRC 2: 0x40 variable 0 IDRC 3: 0x40 variable 0 IDRC --------------------------------- Current Driver State: at rest. --------------------------------- File Number: 0 Record Number: 0 Residual Count 0
Can I manually configure a mode that would have better performance characteristics? Thanks for any tips you might have,
David
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