It seems that ordinary Western Digital (WD) hard drives have an “advanced” feature that makes them unsuitable for either hardware or software RAID. Since I like to mirror the family's hard drives for security in the event of hard drive failure — we had one fail on my wife's machine last week so this is hardly paranoia — this is something I am glad I found before placing an order.
Western Digital manufactures desktop edition hard drives and RAID Edition hard drives. Each type of hard drive is designed to work specifically in either a desktop computer environment or on RAID controller.
If you install and use a desktop edition hard drive connected to a RAID controller, the drive may not work correctly unless jointly qualified by an enterprise OEM. This is caused by the normal error recovery procedure that a desktop edition hard drive uses.
When an error is found on a desktop edition hard drive, the drive will enter into a deep recovery cycle to attempt to repair the error, recover the data from the problematic area, and then reallocate a dedicated area to replace the problematic area. This process can take up to 2 minutes depending on the severity of the issue. Most RAID controllers allow a very short amount of time for a hard drive to recover from an error. If a hard drive takes too long to complete this process, the drive will be dropped from the RAID array. Most RAID controllers allow from 7 to 15 seconds for error recovery before dropping a hard drive from an array. Western Digital does not recommend installing desktop edition hard drives in an enterprise environment (on a RAID controller).
I think the box should have a warning sticker about this…
Meanwhile, back to the hunt for reliable, very quiet, low-heat-producing, mass storage.