3Ware 3W-6800 - Escalade 6800 RAID Controller, User Manual

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Troubleshooting
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dancy Check (CRC) for all ATA data that is transferred. If the data
becomes corrupted between the drive and the storage switch (e.g.,
an intermittent cable connection) the storage switch detects this as a
UDMA CRC or cable error. The storage switch 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 storage switch 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 storage switch supports a feature called dynamic sector repair
to allow the unit to recover from certain drive errors that would nor-
mally result in a degraded array situation. For redundant arrays
such as RAID 1, 10 and 5, the storage switch 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 storage switch
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 sec-
tor, 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
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.