1. Backup speed to DAT-tape rotten, ideas?
I have a HP C1533A SCSI DDS-3 tape connected to a P166 running
FreeBSD 3.3 release.
No matter what I do, I can't get the backup speed over 1-2 MB/min.
I've tried dump, pax, and
find . -xdev -depth -print | cpio -o | dd of=/dev/nrsa0 bs=10k etc
I've experimented with blocksizes between 512b and 64k.
I keep looking at iostat, and the transfer rate rises to about
150k/s, then it appears to overrun the tape, the tape clicks
and whirrs a bit, and restarts with a transfer rate of ~5k/s.
What bugs me is that the Backup program supplied with Windows 98
gets a throughput of ~350k/s with the same hardware, without the
clicking and whirring.
Any ideas ?
The SCSI host adapter is an Adaptec 2940, the PC's got 32MB RAM,
only ran X in addition to the backup. No huge servers running.
mt <dev> stat reports that HW compression is on, and that things
look mostly good.
C'mon guys, help me beat Microsoft..
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