Michael Stiller wrote:
Hi list,
i'm developing an application (in C) which needs to write about
1Gbit/s (125Mb/s) to a disk array attached via U320 SCSI.
It runs on Dual Core 2 Xeons @2Ghz utilizing kernel 2.6.22.7.
People regularly report speeds higher than that on the RAID list, and I
can get that order of magnitude speed using dd with 1MB buffers to a
software RAID-0 array or cheap SATA drives. Are you using a decent
controller? Many "RAID" controllers have bandwidth limitations, buffer
size issues, etc. I had some chea "SCSI" arrays which were just SCSI
controllers in from of a bunch of cheap, slow, non-SCSI drives.
I buffer the data in (currently 4) 400Mb buffers and use write(2) in a
dedicated thread to write them to the raw disk (no fs).
I would limit the write size to a MB and see if that helps, regardless
of the buffer size. A circular queue of smaller buffers, like ptbuf, may
perform better.
The write(2) performance is not good enough, the writer threads take to
much time, and i ask you for ideas, howto to boost the write
performance.
Maybe mmaping the disk would work?
I don't think it would help, I'd really try limiting the size of the
write() calls first, assuming your hardware is adequate.
--
Bill Davidsen <[email protected]>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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