Execution units & multi-core processors

[robertdana]

We just upgraded from a single core, single-processor backup server to a server with a quad-core processor.

 

I had hoped Retrospect would take advantage of multiple cores... that two execution units running simultaneously would each run at the same speed as a single execution unit as long as they weren't using the same disks.

 

This doesn't seem to be the case... right now I'm running two different backup set transfers involving completely separate backup sets. If I pause one, the other gets twice as fast (this is especially obvious when watching disk transfer rates in perfmon). The processor utilization (about 40%) remains constant.

 

This suggests to me that while Retrospect is multithreaded to some extent (otherwise it would be stuck at 25% utilization on a quad-core system), it does not seem to utilize more than two processor cores at once, regardless of how many execution threads are running.

 

Is that correct? Are there any plans to change that?

[Lennart_T]

Raw CPU power is rarely the bottleneck for Retrospect. It shuffles data, not computes it.

[robertdana]

Unless (as in our case) we're talking about compressed and encrypted backup sets. Then it is definitely and provably CPU bound.

[Lennart_T]

I see.

We use only hardware compression in our tape stations, not in our "Disk Backup Sets".

 

You may want to look into this thread about hardware compression/encryption:

http://forums.dantz.com/showtopic.php?tid/27848/