Greetings, I have an old but reliable Intel SE440BX-2 with 440BX and PIIX4E chipset. 120 + 80 GB hard drives on each channel as master, very disappointing md software RAID0 or RAID1 performance.
Slackware 10.1 with 2.4.29 or 2.4.30pre2, testing back to 2.4.21. One thing I noticed is that if I start a dd if=/dev/zero bs=4k of=/dev/hdX on each drive, then Ctrl-C stop each, one terminal will wait for the other drive to complete the write before starting its turn to complete the pending write. It seems that somewhere what I expected to be two parallel data streams are serialised. As the chipset only does udma33 I was hoping to get an OS performance gain with RAID0. Box has 512MB memory and rarely touches swap. Is this a limit of the hardware or did I miss some kernel tuning? Have benchmarked with tiobench -- that tells me chunk-size has little effect, software RAID costs about 8% CPU, and sequential writes cost roughly 20%, 40% and 60% for ext2, ext3 and reiserfs. Filesystem sequential read speed improved from 17 to 25 MB/s for RAID0, but no improvement in write speed. Raw (non-filesystem) dd speeds are about 27MB/s read, 20MB/s write to non-RAID partition. All testing done on same partitions, so no confusion with fast or slow end of drive. The drives are Seagate 7200.7 series with 2MB cache. Any pointers on tuning options appreciated, the Intel datasheets don't really tell me much. As for reading the kernel source, I have no idea where to start, not much under Docs, and I dunno which or which way to turn the 'knobs'. Even search terms would be welcome :) Thanks, Grant. - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
