SOFTWARE-RAID-TIPS (was: Adaptec 7890 and RAID portIII RAID contr

[Mike Bilow]

Many people wrote in messages to Mike Bilow:

 > No, many manufacturers disable AWRE on their drives by default. 
 > I have no idea why, but one must go into the mode pages 
 > manually with a tool such as "scsiinfo" to flip the bits if one 
 > wants AWRE enabled.

 MP> Sorry for the ignorance, but what's AWRE? I didn't find it
 MP> in the scsiinfo man page.

The relevant documentation is the SCSI-2 standard.  From 8.3.3.6:

     An automatic write reallocation enabled (AWRE) bit of one indicates that 
     the target shall enable automatic reallocation to be performed during 
     write operations.  The automatic reallocation shall be performed only if 
     the target has the valid data (e.g., original data in the buffer or 
     recovered from the medium).  The valid data shall be placed in the 
     reallocated block.  Error reporting as required by the error recovery 
     bits (EER, PER, DTE, and DCR) shall be performed only after completion of 
     the reallocation.  The reallocation operation shall report any failures 
     that occur.  See the REASSIGN BLOCKS command (8.2.10) for error 
     procedures.

     An AWRE bit of zero indicates that the target shall not perform automatic 
     reallocation of defective data blocks during write operations.

Anyone actually trying to use scsiinfo to manipulate bits on this level had
best know very well what they are doing and have a copy of the SCST standard.
 
-- Mike




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