Chapter 9. Maintaining Units186 3ware 9550SX Serial ATA RAID Controller User GuideVerifying UnitsFor redundant units, verify checks the redundancy of the unit. For example itwill check parity for a RAID 5 or check data consistency for a RAID 1. If theunit you checked is not a redundant unit, verify performs a surface scan of themedia. During verification, I/O continues normally, but with a slightperformance loss, depending on your verify rate setting. For more detailsabout how verification works, see “About Verification” on page 172. Fordetails about verify rates, see “Setting Background Task Rate” on page 175.For 9000 series controllers, if the verify unit process determines that themirrored drives are not identical or the parity is not correct, the error iscorrected. For RAID 1 and 10, this involves copying the miscompared datafrom the lower port(s) to the higher port(s) of the mirror. For RAID 5 thisinvolves recalculating and rewriting the RAID 5 parity that was incorrect.AEN 36 (“Verify detected and fixed data/parity mismatch”) is posted tothe Alarms page.When this occurs for 7000/8000 series controllers, AEN 36 (“Verifydetected and fixed data/parity mismatch”) is logged and the entire unit isinitialized. For RAID 1 and 10, initialization involves copying the data fromthe lower port(s) to the higher port(s) of the mirror. For RAID 5 this involvesrecalculating and rewriting the RAID 5 parity for the entire unit. If the unit isnot redundant, a file-system check is recommended to correct the issue. If theerrors persist and cannot be overwritten from a backup copy, perform a finalincremental backup. You will need to replace the defective drive, recreate theunit, and reinstall the data.Note: If the unit has not previously been initialized and youmanually select Verify Unit in either 3BM or 3DM, theinitialization process starts.Verification of units can be done automatically, on a schedule, or can bestarted manually, as described below. For information about scheduling, see“Scheduling Background Tasks” on page 176.You can manually start a verify through either 3DM or 3BM. as describedbelow.
