Can't make two partitions the same size

lucmove · 07-30-2011, 05:58 PM

I have a 320GB HDD. I buy a new 640GB HDD. I want to clone my existing partitions in the new HDD then copy everything over.

I do it the way I always do: I run 'cfdisk /dev/sda' in one terminal and check the size of each partition, then I run 'cfdisk /dev/sdb' in another terminal, where I create the partitions, all same size, in the new HDD. Of course, a huge space is left at the end, roughly 320GB.

My partition clone method is not as accurate as I thought it would be. I just copied all the data from my 90GB partition with rsync and noticed the following:

Code:

# df -h
/dev/sda5    83G	    82G	     1.6G     99%  /source
/dev/sdb5    83G	    81G	     1.1G     99%  /target

Uh oh. The newer partition somehow (shrug) uses less space, but it also has less space available. Let me have a close look:

Code:

# df
/dev/sda5    86599506    84966076    1633430  99%  /source
/dev/sdb5    86584210    84646734    1057607  99%  /target

So what am I doing wrong, what would the correct way to do it have been?

jefro · 07-31-2011, 12:45 PM

I think you can use fdisk or maybe that but instead of selecting a % you select start and end cylinders.

catkin · 08-01-2011, 02:21 AM

Possibly caused by cfdisk rounding a setting in MB to suit the HDD's characteristics ... ?

You could try using cfdisk's Units facility to set identical sizes in sectors (but this may yield a sub-optimal layout ...?).