LTO tape drive speed slow on Redhat 4

[Pauli Borodulin]

mcclnx mcc wrote:
> We have IBM LTO tape drive connect to DELL 6800
> server.  This server has Redhat AS 4.3 installed.  

> Initially I test "tar cvf /dev/st0 .", it can ONLY
> perform 4MB/sec speed.  After I disbale "direct I/O"
> on ST, the speed up to 9MB/sec.

> LTO tape drive speed supposely should around 15MB/sec
> -30MB/sec.  does anyone know how to make it run
> faster?

By default, Tar uses block size of 20*512B = 10kB. This is really small and
is a probable reason for your slowness. Most LTO systems in use operate most
efficiently with a 64kB blocksize, so try using that instead. First
configure the drive for variable block size by running "mt setblk 0" (you
may need to define the device with the -f parameter). Then use "tar -b128
..." to make the tar archives. It is also necessary to use the same
parameters when reading the tapes.


Br,
-- 
Pauli Borodulin <pauli.borodulin at uta.fi>
Systems Analyst, tel. +358 3 3551 7892
Computer Centre / Room B4179
University of Tampere, Finland