Tape xfers topping out at 10K per transaction?
Kevin A. Pieckiel
pieckiel at sdf.lonestar.org
Thu Oct 7 03:50:56 PDT 2004
On Wed, Oct 06, 2004 at 10:24:16PM -0500, Dan Nelson wrote:
> In the last episode (Oct 06), Kevin A. Pieckiel said:
> > I've got an Exabyte M2 connected to my system. I'm running version
> > 5.2.1 and have seen this drive do 64K transfers with "systat -vm"
> > before (although that was under version 4.9). I can't for the life
> > of me find out why I'm only getting 10K per transaction while I'm
> > reading from my tape now. At the rate it's going, it will take over
> > 10 hours to read through the entire thing. I know the tape drive is
> > capable of reading an entire tape in about three hours.
> Tar defaults to a 10k blocksize. When creating tapes, use the 'b'
> flag to specify blocksize in 512-byte units. For a 64k blocksize:
> "tar cvbf 128 /dev/sa0 /usr"
I hit the same 10K limit when I use something like this:
# dd if=/dev/nsa0 of=/dev/null bs=64k
Is that because tar wrote to the tape with a 10k bock size that even
dd can't read larger blocks? That doesn't seem likely to me, but
then again, what do I know?
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