Rebuild Command (81H) - Seagate SCSI Interface Product Manual

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5.28

Rebuild command (81h)

The Rebuild command (Table 135) requests that the target write to the medium the Xor data generated from
the specified source devices. The target, acting as a temporary initiator, issues Read commands to retrieve the
specified data from the source device. For additional information about Xor commands, see Section 5.55.1.
Note. The target that receives the Rebuild command is not one of the source devices. If only one source is
specified, then an Xor operation does not occur. This case can occur in disk mirroring applications.
If the command terminates with Check Condition status the sense data shall contain the logical block address
of the failed block with the lowest logical block address. All logical blocks affected by the command and having
a logical block address lower than that of the reported failing block shall be rebuilt and written to the medium.
Table 135: Rebuild command (81h)
Bit 7
Byte
0 Operation Code (81h)
1
2 (MSB)
3
4
5
6 (MSB)
7
8
9
10 (MSB)
11
12
13
14 Reserved
15 Control [8]
Notes.
[1] If the Disable Page Out (DPO) bit is set to one, no data is cached. The DPO bit is only meaningful if the
RCD bit of Mode Select Page 8 is set false (caching enabled).
[2] A Force Unit Access (FUA) bit of one indicates that the Write command shall not return Good status until
the logical blocks have actually been written on the media. The FUA bit is only meaningful if the WCE bit
of Mode Sense page 8 is true.
[3] If the Intermediate Data (IntData) bit is set to zero, then intermediate data is not sent with the Rebuild
parameter list. If the bit is set to one, the Rebuild parameter list includes Intermediate Data. The length of
the intermediate data can be calculated by multiplying the rebuild length times the block size. This data
shall be treated as an additional source, and an Xor operation performed with it and the data from the
specified sources.
6 5
Reserved
SCSI Interface Product Manual, Rev. J
4 3
DPO [1] FUA [2]
Logical Block Address [5]
Rebuild Length [6]
Parameter List Length [7]
2 1
IntData [3] Port Control [4]
0
(LSB)
(LSB)
(LSB)