And of course it's even worse if you have compressible data. Since it's
uncompressible once encrypted, you can't let the tape drive handle it... So in
our case, on a quad-core server, we see a single core saturated apparently
doing both the compress and encrypt routines, while 3 cores idle. Leads to
much slower backup times than it would otherwise be capable of. Even having
one core compress and another encrypt would be more efficient in our case.
________________________________________
From: Richard Scobie [richard AT sauce.co DOT nz]
Sent: Sunday, March 28, 2010 11:26 AM
To: bacula-users
Subject: [Bacula-users] Possibility of parallelising encryption?
I have a 2.8GHz Core i7 machine backing up uncompressable data spooled
onto an 8 drive RAID5, to LTO-4 tape.
Our requirements now dictate that data encryption must be used on the
tapes and having configured this, it seems that one core is saturated
encrypting the data and the result is that tape write speed is now about
50% slower than when encryption is not used.
Would it be possible to optimise this task by perhaps reading data in
"chunks", which in turn can be encrypted by a core each, before being
recombined and written out to tape?
I'd use the hardware encryption (which presumably has no performance
impact), that is an option on this autochanger, except they want $2500
for it...
Regards,
Richard
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Try the new software tools for yourself. Speed compiling, find bugs
proactively, and fine-tune applications for parallel performance.
See why Intel Parallel Studio got high marks during beta.
http://p.sf.net/sfu/intel-sw-dev
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