[CentOS] Performance Issues

Tue Sep 4 16:07:44 UTC 2007
Joshua Baker-LePain <jlb17 at duke.edu>

On Sun, 2 Sep 2007 at 8:11am, Dan Dansereau wrote

> We have a DELL6850 with 8Gbytes of memory,  four 3.2Ghz CPU's , perc 4
> raid controller, with fourteen 300Gbyte 10Krpm disk on a powervault
> 220s, And a powervault 124T  LTO-3 tape systems on a separate
> 160Mbyte/sec adaptec SCSI card.

Which card and driver?  ISTR folks having issues with adaptec cards and 
LTO3 drives.  Might you have a spare LSI SCSI card (ultra320, preferably) 
about that you could test with?

> The disks are configured as two 2Tbyte raid 0 partitions using the perc
> 4 hardware.
> The problem is - reading from the disk, and writing to the tape is
> pathetically slow.
> The specs say I should get around 80Mbyte/second - in reality - is about
> 500 Kbytes/second

Have you benchmarked the disks to make sure you get decent performance out 
of them?

> Writing just to tape, using /dev/zero as input and dd to write, I can
> get up to 60Mybte/second, indicating that the tape drive and scsi card
> is functional from a hardware perspective. Since I can read and write
> data to the disks - I assume that they are functional.
> The files are 80Mybtes for the minimum size that I am writing to tape.

80MB total or lots of 80MB files?  If the former, you really need to test 
with, IMO, at least 2X RAM (preferably 4X) sized data to get a reliable 
speed estimate.

> Is there a standard disk / tape IO test package that could test the
> speed/performance of the disks and /or tapes?

bonnie++ is somewhat standard for testing disk sequential read/write 

Joshua Baker-LePain
Department of Biomedical Engineering
Duke University