On Wed, 15 Jul 2009, Richard Elling wrote:
Unfortunately, "zpool iostat" doesn't really tell you anything about performance. All it shows is bandwidth. Latency is what you need to understand performance, so use iostat.
You are still thinking about this as if it was a hardware-related problem when it is clearly not. Iostat is useful for analyzing hardware-related problems in the case where the workload is too much for the hardware, or the hardware is non-responsive. Anyone who runs this crude benchmark will discover that iostat shows hardly any disk utilization at all, latencies are low, and read I/O rates are low enough that they could be satisfied by a portable USB drive. You can even observe the blinking lights on the front of the drive array and see that it is lightly loaded. This explains why a two disk mirror is almost able to keep up with a system with 40 fast SAS drives.
This is the opposite situation from the zfs writes which periodically push the hardware to its limits.
Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
