I'm not sure what the most efficient blocking factor is for this tape, but
the default I think is 1, which is bad.
On Exabyte 8mm tapes, which AIT2 is eventually derived from, we used to
use a blocking factor of 100000, if I recall.
A small blocking factor takes more time, and wastes more tape, since there
is an inter-block gap between each tape block.
The larger blocking factor means the driver has to buffer more memory,
which is wired from the kernel. Too big used to be bad. But most systems
have comparatively infinite amounts of memory now.
We used to send everything through dd, but gtar might have a blocking
option...
Hope that helps.
--Dean
On Mon, 9 Dec 2002, Dave Belfer-Shevett wrote:
>
> This is like a question I'd send to ye-ole sun-managers list, but here
> goes.
>
> I have an AIT2 drive on an E250 that I need to dump about 300gig of data
> to. The AIT2 specs say that with a compressed volume (/dev/rmt/1c) I
> should get about 120 gig on a single tape.
>
> So far so good.
>
> The problem is, the write speed is PAINFULLY slow. We're using gnutar,
> and the command is:
>
> tar -c -M -f /dev/rmt/1c -L 120000000 .
>
> With that command its taking 8-12 HOURS to run a single tape. Not good.
>
> I'm guessing a blocking factor problem. Any ideas what an appropriate
> blocking factor for this arrangement should be?
>
> Thanks!
>
> -dbs
>
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