Replacing Drive with SSD

Brandon J. Wandersee brandon.wandersee at
Fri Aug 28 17:37:47 UTC 2015

Matt Smith writes:

> I've heard a rumour that you should never use dd with SSD drives because 
> of the wear levelling stuff. Apparently SSDs automatically make sure 
> that data is sent to unused flash cells so that all the cells wear 
> evenly, but if you use dd on them it makes them think that every single 
> cell is in use which screws this up?

I've read the same thing before, but I can't imagine it would really be
a problem if it's the first thing you do with a new disk (and the only
time you do it). Personally, though, I would just avoid using dd.

If you're making a 1:1 clone of a system--if you're copying the same
partition scheme to a newly purchased disk of the exact same make and
model--then dd is fine, but since dd can't account for partition size or
alignment, differences in block/cylinder count, filesystem settings (you
should activate TRIM and eschew SU+J *before* copying a large amount of
data over) and what-not, it's best to just create new partitions and
filesystems and use the dump/restore method.

   		      :: Brandon Wandersee ::
                  :: brandon.wandersee at ::
'A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
                            			- Douglas Adams

More information about the freebsd-questions mailing list