On 06Sep2018 21:25, Fred Smith <fredex(a)fcshome.stoneham.ma.us> wrote:
On Fri, Sep 07, 2018 at 11:10:08AM +1000, Cameron Simpson wrote:
> On 06Sep2018 19:20, Ranjan Maitra <maitra(a)email.com> wrote:
> >I have two drives mounted on a F28 system. Both are identical 4TB
> >drives. The second one is empty. I am concerned about the first
> >one failing so would like to copy the contents (which are around
> >3.7 TB) to the second.
> >What is the fastest way to copy the contents of the first drive to
> >the second? I was using rsync, but is there a better way?
while the other suggestions might be faster, I prefer to use dd
(or ddrescue) 'cause it gives a bit-for-bit copy of everything
on the drive, partitions and all. ddrescue is handy in case it
finds spots that are hard to read on the source drive, it goes
back and retries them til it gets a good read.
If the discs aren't full (or close to full) this should be slower. It does have
the advantage of doing sequential drive I/O, so minimal drive head stepping.
Downsides: drives must be exactly the same size. If you're doing this with a
partition (safer) the same size constraint applies (well, the target area can
be bigger and you can resize the filesystem afterwards, depending on the
If your drives are good where there's data, dd has some (small) risk of having
an I/O error on nondata (unallocated areas). Tedious and annoying.
The other advantage of a file based copy (cp, rsync, tar etc) is that you can
seize the opportunity to switch filesystems, eg upgrading from ext3 or ext4 to
Cameron Simpson <cs(a)cskk.id.au>