des at ofug.org
Sun Mar 30 08:10:42 PST 2003
Lukas Ertl <l.ertl at univie.ac.at> writes:
> I'm currently testing with prime stripe sizes, but it doesn't seem to
> help. I additionally added "options AHC_ALLOW_MEMIO" to the kernel, and it
> has raised write performance in the single-disk case (although I'm not
> happy with that one either; I expected a disk on a U160 controller to pump
> out more than ~65MB/s).
Does the data sheet for your disk indicate that it can in fact write
much faster than that? The speed at which data is actually written to
the media is much lower than the bus speed - the bus speed *has* to be
higher to accomodate multiple devices.
For instance, the "internal formatted transfer rate" for a recent 73GB
Seagate Cheetah varies between 38.4 and 63.9 MB/s (depending on how
far out from the spindle you're writing). You won't see higher
average transfer speeds than that unless the data you're writing fits
entirely within the disk's on-board cache.
Dag-Erling Smørgrav - des at ofug.org
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