Performance with Embedded Array Controller

[tdeneau1]

I inherited some DL360 systems which had P440ar Smart Array controller to which the OS drive and 7 data drives were attached.  I wanted to experiment with the embedded controller instead so I moved the drives there.  (the P440ar was still in the system just nothing connected).

When I measured dd performance using reads with iflag=direct, performance was as I expected, in fact was similar to using the P440ar in HBA mode.  However, when I tried dd writes with oflag=direct, performance was terrible (less than 10 MB/s).

Is there some configuration issue I am missing?

[Edwin Eppel]

The embedded controller has no cache while the P440ar should have a write-behind cache. That's going to have some impact on performance.

[tdeneau1]

The test I was using was running

dd of=/dev/sdb2 if=/dev/zero oflag=direct bs=64K count=10000

Since I am using oflag=direct, I would have thought that would take the cache out of the picture.  On other no-cache controllers on other systems I have seen approximately 140 MB/sec with these same drives

[Dennis Handly]

> I would have thought that would take the cache out of the picture. 

That's probably just the OS cache.