Copy SCSI disk including, if any, the first cylinder

[Davis Johnson]

Michal Jaegermann wrote:

>On Sat, Dec 17, 2005 at 11:24:51AM -0800, Bob Taylor wrote:
>  
>
>>I have a failing SCSI disk in my LX164. I need to copy it *totally* onto
>>a SCSI disk of the same size. I know how to copy all the files but I
>>don't know if there is any boot stuff located on the first cylinder
>>other than the BSD label
>>    
>>
>
>If this is a boot disk then you have also a boot block.  It could be a
>better idea to write a new one using swriteboot instead of copying
>whatever can be copied from a failing disk.
>
>In general 'dd', which has various options, can be used to copy
>bit-by-bit whole disks or parts of those.  If your source disk is
>failing then you may need to use 'conv=noerror' to get anywhere with
>such copy; but that means that on your target you may get blocks of
>zeros instead of the real data and if that will cause only limited or a
>massive damage depends purely on your luck.
>
>   Michal
>  
>
Of course the best option is to have just completed a full backup just 
before the disk started to fail.

If dd works, and another similar (or larger) disk is available it is a 
relativly painless process.

   1. Physicly configure the replacement disk into the system
   2. use dd to copy from the failing disk to the replacement disk
   3. remove the failing disk from the system
   4. Remove the failing disk from the system
   5. Configure the replacement disk to physicaly replace the failing disk.

There is no need to worry about partitioning the replacement disk or 
making it bootable. This can save time and effort.

Those ifs are important tho, your suggestion about conv=noerror is a 
good one. Sometimes (frequently?) a failing disk will still cough up the 
data, but you may be logging excesive retrys.

Sometimes if a disk is realy dodgy your only option is to rebuild what 
you must from other sources (renstall) and concentrate your efforts on 
selectivly copying off just the most important files.