On Mon, 13 Oct 2008 14:07:15 -0700 "Grant Grundler" <grundler@xxxxxxxxxx> wrote: > On Mon, Oct 13, 2008 at 12:19 PM, kenneth johansson <ken@xxxxxxxxx> wrote: > > When writing data to /dev/sdb (that is the whole disk and no filesystem) > > it starts out ok around 100MB/sec but soon end up doing considerably > > worse. For prolonged times lasting several minutes it hovers in the > > 20-30MB/sec. > > Is the application using "O_DIRECT"? > If not, could be issue with how VM writeback is (not) working. Or just mashing up the I/O horribly. Would also be worth turning the CFQ scheduler off or applying Arjan van de Ven's patches to fix the ioprio of the kernel writeout threads. That last patch makes a huge difference here. Alan -- 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
