multisecond hang in getdents Linux 2.4, x86, ext3fs

I'm seeing a strange performance problem on one of our systems. When running a find on one filesystem, there are long hangs (up to 30 seconds plus) during the find. Strace reveals that some of the getdents calls are taking that much time!

From 'strace -T':

Oddly enough, not all of them are taking so long:

The system is otherwise almost completely idle during the find. Nothing else is putting much of a demand on the filesystem. As you can see, the time the getdents takes does not seem to be a function of how much it returns. None of the directories the find traverses have very many entries - none have more than 100, even. During the hang, vmstat shows a blocked process, but no time spent in iowait. Any attempt to access the same filesystem during a hang also hangs, so it's not just the one process. The hangs are not repeatable at the same directory - if I try just running a find at the point where a find hung before, it's more likely than not to proceed just fine.

The filesystem is ext3, on a mirrored pair of Maxtor 180 GB SATA drives attached to a 3Ware 8500-4. The 3Ware software does not show any problems with the mirror. These are the only drives in the system, so I can't directly compare them against anything else. Nothing out of the ordinary appears in dmesg orvar-log-messages. I'm pretty out of ideas...the length of time feels like an ATA timeout to me, but I don't have any real evidence for that. Any suggestions would be much appreciated.

JDW