On Fri, Sep 01, 2006 at 10:32:12PM +0900, Tejun Heo wrote: > ># dd if=/dev/zero of=/dev/sda1 bs=4M count=512 > > > >avg-cpu: %user %nice %sys %iowait %idle > > 0.90 0.00 1.30 97.80 0.00 > > > >Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn > >sda 15.00 0.00 1920.00 0 19200 > > Hmm... this really is weird. FYI, you're the first to report such > problem. As Jeff said, turning off write-back caching can have adverse > effect on write performance, but, then again, you previously reported > that the command queue is full. Please update us on the write-back stuff. >From searching the list archive, I gather this is controlled by "hdparm -W"? root@linux-srv:~ # hdparm -W 1 /dev/sda1 /dev/sda1: setting drive write-caching to 1 (on) root@linux-srv:~ # dd if=/dev/zero of=/dev/sda1 bs=1M count=100 100+0 records in 100+0 records out 104857600 bytes (105 MB) copied, 53.8702 seconds, 1.9 MB/s root@linux-srv:~ # hdparm -W 0 /dev/sda1 /dev/sda1: setting drive write-caching to 0 (off) root@linux-srv:~ # dd if=/dev/zero of=/dev/sda1 bs=1M count=100 100+0 records in 100+0 records out 104857600 bytes (105 MB) copied, 53.7884 seconds, 1.9 MB/s I'm going to try narrowing the scope of the test next. Will purchase an eSATA<->SATA cable today and try bypassing the port multiplier. If that works, I'll try using one drive at a time on the PMP. Thanks, Derek - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
