Re: Slow writing speed on LTO4 SAS tape SOLUTION

On Wed, 24 Feb 2010 16:08 -0300, "Ciro Iriarte" <[email protected]>
wrote:
> 2010/2/24 Silviu Marin-Caea <[email protected]>:
> > On Wed, 24 Feb 2010 10:33 +0100, [email protected] wrote:
> >> Just a thought:
> >>
> >> How fast can you read from the source ?
> >
> > Fast, it's a RAID with 6 disks.
> 
> Hmmm, just to make sure, do a test reading from memory.
> 
> dd if=/dev/zero of=/dev/st0

I knew about /dev/st0 (rewinding tape device) and /dev/nst0
(non-rewinding tape), but access to this kind of obscure information in
my head is slow (one day, a good night sleep cycle).

Look:
tar --blocking-factor=2048 --totals --create --file /dev/nst0
4GofGarbage
Total bytes written: 4296015872 (4.0GB, 69MB/s)

If you use /dev/st0, the time it takes to rewind, automatically, by
default, after writing will make you compute erroneously the writing
speed.

69 MB/s is still far from the theoretical 120 MB/s but not quite as far
as 15 MB/s
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