Abysmal UFS performance on SB1K...

From: UNIX Museum (unixmuseum_at_verizon.com)
Date: 09/30/05 

Date: Fri, 30 Sep 2005 03:46:09 GMT

Hi there,

I am trying to understand why my SB1K gives me abysmal performance on
sequential read/write...

My setup is 2x15,000RPM 36GB drives, Solaris 10. I run the Nastran FEA
solver, which sometimes creates huge scratch files that are constantly
accessed... I direct all my scratch files on my second drive... I am
seeing some very long solve time compared to much slower machines.

An example would be SB1K 2x900 being 3 times slower than an sgi Octane2
2x400 for solves that use extensive I/O. For solves with little I/O, the
SB1K is about twice the speed of the Octane2, which is what I expected.
It is not limited to Nastran, other FEA solvers show the same trend...

So, it appears to me that the culprit is the scratch filesystem... I
tried to mount the drive with forcedirectio, but it looks like it made
things even worse... Does anybody have any suggestion?

Somebody on the Sun Hardware forum was saying that this is because the
drives weren't Sun drives, therefore the performance should suck, or at
least wouldn't be as good as it should, with actually no way of making
it any better... Has anybody seen this?