3Ware 9550SX-4LP User Guide - Page 241

AEN Messages 020h Prepare for shutdown (power-off) 021h Downgrade UDMA mode The 3ware RAID controller communicates to the ATA disk drives through the Ultra DMA (UDMA) protocol. This protocol ensures data integrity across the ATA cable by appending a Cyclical Redundancy Check (CRC) for all ATA data that is transferred. If the data becomes corrupted between the drive and the 3ware RAID controller (e.g., an intermittent cable connection) the 3ware RAID controller detects this as a UDMA CRC or cable error. The 3ware RAID controller then retries the failed command three times at the current UDMA transfer rate. If the error persists, it lowers the UDMA transfer rate (e.g., from UDMA 100 to UDMA 66) and retries another three times. This AEN is sent to the user when the 3ware RAID controller lowers the UDMA transfer rate. Possible causes of UDMA CRC errors are bad interface cables or cable routing problems through electrically noisy environments (e.g., cables are too close to the power supply). 022h Upgrade UDMA mode During the self-test, if a drive is found to not be in the optimal UDMA mode, the controller will upgrade its UDMA mode to be optimal. 023h Sector repair completed The 3ware RAID controller supports a feature called dynamic sector repair to allow the unit to recover from certain drive errors that would normally result in a degraded array situation. For redundant arrays such as RAID 1, 10, 50, and 5, the 3ware RAID controller essentially has two copies of the users data available. If a read command to a sector on a disk drive results in an error, it reverts to the redundant copy in order to satisfy the host's request. At this point, the 3ware RAID controller has a good copy of the requested data in its cache memory. It will then use this data to force the failing drive to reallocate the bad sector, which essentially repairs the sector. When a sector repair occurs, the user is notified by this AEN. The fact that a sector repair AEN has been sent to the user is an indication of the presence of grown defects on a particular drive. While typical modern disk drives are designed to allow several hundred grown defects, special attention should be paid to any drive in an array that begins to indicate sector repair messages. This may be an indication of a drive that is beginning to fail. The user may wish to replace the drive, especially if the number of sector repair errors exceeds 3 per month. www.3ware.com 231