Re: RAID 5 performance problems

[Peter L. Ashford]

Stephan,

> here benchmark from my system with an fasttrak-tx4 (same card jonathan
> has) with WD1800BB :

The WD1800BB and the WD1200BB use the same technology (same data density,
fewer platters).  The streaming speed should be very similar.

> /dev/hde:
>  Timing buffer-cache reads:   128 MB in  0.28 seconds =457.14 MB/sec
>  Timing buffered disk reads:  64 MB in  1.37 seconds = 46.72 MB/sec
>
> WD1800BB on onboard ultra100 controller :
>
> /dev/hdo:
>  Timing buffer-cache reads:   128 MB in  0.28 seconds =457.14 MB/sec
>  Timing buffered disk reads:  64 MB in  1.58 seconds = 40.51 MB/sec
>
> WD1800BB on onboard ultra33 controller :
>
> /dev/hda:
>  Timing buffer-cache reads:   128 MB in  0.28 seconds =457.14 MB/sec
>  Timing buffered disk reads:  64 MB in  2.55 seconds = 25.10 MB/sec

OK.  We've found a potential issue.  Are the disks being identified as
UDMA-33 or UDMA-66/100/133?  The performance numbers agree too closely for
this to be a coincidence.  Check the boot logs.

Good luck.
				Peter Ashford