On Jun 17, 2011, at 7:06 AM, Edward Ned Harvey <opensolarisisdeadlongliveopensola...@nedharvey.com> wrote:
> I will only say, that regardless of whether or not that is or ever was true, > I believe it's entirely irrelevant. Because your system performs read and > write caching and buffering in ram, the tiny little ram on the disk can't > possibly contribute anything. You would be surprised. The on-disk buffer is there so data is ready when the hard drive head lands, without it the drive's average rotational latency will trend higher due to missed landings because the data wasn't in buffer at the right time. The read buffer is to allow the disk to continuously read sectors whether the system bus is ready to transfer or not. Without it, sequential reads wouldn't last long enough to reach max throughput before they would have to pause because of bus contention and then suffer a rotation of latency hit which would kill read performance. Try disabling the on-board write or read cache and see how your sequential IO performs and you'll see just how valuable those puny caches are. -Ross _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
