[SATLUG] RAID5 & ddrescue

Herb Cee hc at lookcee.com
Sun Aug 23 10:53:32 CDT 2009


David Labens wrote:
> First, since none of the data drives were mounted, I shut down the server and removed all the data drives except /dev/sdc.  Then, I installed the new drive on the cable that had /dev/sda.  
>
> Then, I ran fdisk and created a new primary partition.  Strangely enough, it would only allow me to create /dev/sda, not /dev/sdf that I WANTED to create, just to prevent confusion.  But, confusion had already set in.
>
> Then, I went to use ddrescue:
> ddrescue --no-split /dev/sdc /dev/sda logfile
>
> Strangely enough, it quit after 80 gb was copied.  So, I examined the drives and found that /sdc was no longer the bad drive, but was now my 80 gb OS drive, and my bad drive was now /sdb (by examining & comparing serial numbers).  Fortunately, it had not turned the bad drive into /sda, so my bad data was still intact.
>
> I tried rerunning the command, this time with the proper source drive, but it consistently started running it at the 80 gb point where the first command had stopped.  
>
> So, I had to fdisk to remove the partition, write it to the system & exit, then run fdisk to create the partition & write it to the system & exit.
>
> Here is the current output ...
>
> root at RCH-SERVER:/# ddrescue --no-split /dev/sdb /dev/sda resclog1
>
>
> Press Ctrl-C to interrupt
> Initial status (read from logfile)
> rescued:         0 B,  errsize:       0 B,  errors:       0
> Current status
> rescued:    17471 MB,  errsize:    233 kB,  current rate:   54525 kB/s
>    ipos:    17471 MB,   errors:       4,    average rate:   52466 kB/s
>    opos:    17471 MB
> Copying data...
>
> You can see that there are already 4 errors, but it's still working.
>
> Updates will be forthcoming as progress is made.
>
> But, I DO have a question...  When I go back to reassemble the array (after re-connecting everything), will the system automatically know which /sda is the copy of the /sdc that became the /sdb???
>   
Sorry David kant resist, Whos on first? Yes!
herb



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