I've got a SuSE server with reiserfs formatted partitions, all on a RAID1 mirror. I'm noticing odd spikes in iowait, but generally all seems okay. iostat claims not even 3% iowait in general:

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           6.53    0.03    1.45    2.92    0.00   89.07

After tracking down some odd behaviour when ls'ing, it appears "stat" (ls is aliased to include color which does a stat process on each file) randomly takes 5 seconds on a file in the directory. ReiserFS does a file system sync every 5 seconds, but that's interval between not length of time taken to sync. Out of curiosity I did remount using noatime to see if that would help though as it would reduce sync's workload, but no joy.

Anyone got any thoughts what might be causing this pause? Disks appear healthy, RAID controller believes the RAID is healthy, and io stats show the disks aren't working very hard at all.