zfs i/o hangs on 9-PRERELEASE

[Mark Felder]

Hi all,

Just wanted to report back that I found time to do more diagnostics. 
ZFS/FreeBSD/etc are not to blame. ZFS / FreeBSD never reported any I/O 
errors and scrubs always came up clean because one of the disks was 
failing and had issues reading the disk but would eventually return 
accurate data. It was sort of like having a RAIDZ with one disk that had 
30s latency sometimes! Seatools confirmed this disk was failing and 
after replacing the disk all issues went away.