Unix Tip: WHY MV IS SLOW

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3431 - July 2, 2011

http://www.ugu.com/sui/ugu/show?tip.today

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WHY MV IS SLOW

mv command across filesystems
is slower on large files

WHY?

mv would be slow if you are
moving files across filesystem.

The inode number changes only
when a file is moved across
file system.

A new inode number means a new
file is physically created on
disk.

It remains unchanged, if it
is within the same filesystem.
One can verify by using
ls -il command on that file.

mv uses rename() system call.
if it fails, it uses copy routine
(basicailly reads from a file and
writes in another file).

mv command across filesystem is
more of a copy then mv.

This tip generously supported by: dkotian1@rediffmail.com

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