23 Jun 09 8:38
After using multiple diag programs on raid arrays over the last 20 years, I have yet to find one which works reliably on raid arrays, even if the individual drives are placed on standard drive interfaces for testing. Some diags may pickup bad sectors and will pickup very obvious drive failures, but you would be surprised how many drives will pass all tests, no errors, hanging off a standard disk interface in constant testing for weeks, only to fail once place back into an array. The only reliable testing is with a drive testing hardware device. That said, it could be anyone of the drives which has not been replaced.
This situation could be caused by a bug in the raid adapter firmware, so it should be the most up to date. Less likely, hard drive firmware, unless the drives are certain Seagates models with known issues. Different firmware revisions do not help the situation.
Reseat all cables.
Look at raid management software logs, any drive which has soft/hard errors is more likely an offending drive, then a drive which show no errors.
Pull the drives out with power off, make sure you know which slot each drive comes from, number them with a magic marker... any chips on the drive PCB boards which have abnormal hot spots? examine each drive PCBs carefully.
Chernobyl disaster..a must see pictorial