increasing dd disk to disk transfer rate

[Eric Anderson]

Bakul Shah wrote:

>>Bakul Shah wrote:
>>    
>>
>>>>In the last episode (Jan 12), Christoph Kukulies said:
>>>>        
>>>>
>>>>dd if=/dev/ad2 conv=noerror,sync bs=64k | dd of=/dev/ad3 bs=64k
>>>>        
>>>>
>>>So now on the new disk he has files with random blocks of
>>>zeroes and *no* error indication of which files are so
>>>trashed.  This is asking for trouble.  Silent erros are
>>>worse.
>>>
>>>He ought to do a file level copy, not disk level copy on
>>>unix.  That way he knows *which* files are trashed and can do
>>>      
>>>
>>The problem is, FreeBSD panics when it encounters bad sectors in 
>>filesystem metadata. I had the same situation ~a month ago and gave up, 
>>restoring from old backups. It will also probably panic on corrupted or 
>>zeroed metadata, but at least it's on a readable disk...
>>    
>>
>
>Good point.  Would fsdb help?  If not someone ought to extend it.
>  
>
I think after the dd is done, fsck should be run against the affected 
filesystems, which should take care of most of the issues.

The OP's question was how to make dd faster, not really how to get the 
data across safely. :)

Eric




-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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