Aen_Udma_Downgrade; Aen_Sector_Repair - 3Ware 7000-2 - Escalade RAID Controller User Manual

Troubleshooting
AEN 021h AEN_UDMA_DOWNGRADE
The ATA 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 Redun-
dancy Check (CRC) for all ATA data that is transferred. If the data
becomes corrupted between the drive and the ATA RAID controller
(e.g., an intermittent cable connection) the ATA RAID controller
detects this as a UDMA CRC or cable error. The ATA RAID con-
troller 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 ATA
RAID controller lowers the UDMA transfer rate.
Possible causes of UDMA CRC errors are intermittent or bad ATA
interface cables or cable routing problems through electrically
noisy environments (e.g., cables are too close to the power supply).
AEN 023h AEN_SECTOR_REPAIR
The ATA 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 and 5, the ATA RAID controller essen-
tially 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 redun-
dant copy in order to satisfy the host's request. At this point, the
ATA 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 hun-
dred grown defects, special attention should be paid to any drive in
www.3ware.com 183