On 06Sep2018 19:20, Ranjan Maitra <maitra@xxxxxxxxx> 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?
I like "cp -a", it is faster than rsync. Rsync's strength is incremental
update: make a sweep afterwards with rsync to convince yourself it is correct.
Even faster is a tar pipeline:
cd /drive1
tar cf - . | ( cd /drive2; tar xf - )
because both cp and rsync do one file at a time. There will inherently be small
pauses at each file boundary. Actually, rsync might stream a little.
Using piped tars and many files, particularly many small files, the first tar
can get ahead of the second tar for better throughput - the data queued in the
pipe (which has a buffer, and a generous one on Linux) allows the first tar to
proceed until the pipe is full if the second tar is blocked. (The second tar
will of course be blocked writing to drive2, but it won't be blocked reading
from drive1 because the first tar can read followon files from drive1 which the
second tar reads from the pipe).
However, if you're already a significant way through your copy you may as well
stick with rsync unless you can easily do things in chunks, as changing systems
means wasting time copying already copied data. Do a "df" and make an estimate.
If there are still hours to go you could consider switching methods and doing
the uncopied subdirectories:
cd /drive1
tar cf - uncopieddir1 uncopieddir2 ... | ( cd /drive2 ; tar xf - )
and then come back with rsync afterwards to clean up the rest:
rsync -iaP /drive1/ /drive2/
Cheers,
Cameron Simpson <cs@xxxxxxxxxx>
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