On May 11, 2007, at 9:09 AM, Bob Netherton wrote: **On Fri, 2007-05-11 at 09:00 -0700, lonny wrote: **I've noticed a similar behavior in my writes. ZFS seems to write in bursts of ** around 5 seconds. I assume it's just something to do with caching?
^Yep - the ZFS equivalent of fsflush. Runs more often so the pipes don't ^get as clogged. We've had lots of rain here recently, so I'm sort of ^sensitive to stories of clogged pipes. ^ **Is this behavior ok? seems it would be better to have the disks writing ** the whole time instead of in bursts. ^ ^Perhaps - although not in all cases (probably not in most cases). ^Wouldn't it be cool to actually do some nice sequential writes to ^the sweet spot of the disk bandwidth curve, but not depend on it ^so much that a single random I/O here and there throws you for ^a loop ? ^ ^Human analogy - it's often more wise to work smarter than harder :-) ^ ^Directly to your question - are you seeing any anomalies in file ^system read or write performance (bandwidth or latency) ? ^Bob No performance problems so far, the thumper and zfs seem to handle everything we throw at them. On the T2000 internal disks we were seeing a bottleneck when using a single disk for our apps but moving to a 3 disk raidz alleviated that. The only issue is when using iostat commands the bursts make it a little harder to gauge performance. Is it safe to assume that if those bursts were to reach the upper performance limit that it would spread the writes out a bit more? thanks lonny This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
