On 2006-05-02 16:17, Guy Dallaire wrote:
Hi,
Recently added an Overland LoaderXpress LTO 2 tape library to my setup.
Inside the loader is an OEM HP Ultrium tape drive. My tape server is a
centos 4.2 box (RHEL 4 clone)
I'm using software compression with amanda 2.4.5p1 already.
Problem is, the tape drive in the library always seems to have hardware
compression ON. There is no way on the library operator panel to force
the compression OFF.
How did you find out? Used "amtapetype -c"? (just curious)
I've heard that LTO2 drives can easily cope with already compressed data
(and do not try to re compress it). Is this true ? Otherwise, I fear
that trying to compress already compressed data might actually use more
tape space and reduce throughput.
I've searched the amanda wiki and di not find anything.
Yes, leaving HW compression for LTO drives does not hurt.
In fact, I have exactly the same, and have hw-compression on, so that
those few DLE's that have no compression enabled (because they are too
slow), can benefit from hw-compression, giving me a few extra bytes on
the tapes.
http://wiki.zmanda.com/index.php/Tapetype_definitions#HP448_.28LTO_Ultrium2.29_with_200.2F400_Gbyte_tapes
--
Paul Bijnens, xplanation Technology Services Tel +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM Fax +32 16 397.512
http://www.xplanation.com/ email: Paul.Bijnens AT xplanation DOT com
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