[Asterisk-Users] MeetMe Features

[Peter Svensson]

On Fri, 10 Dec 2004, Christopher L. Wade wrote:

> > I don't think I quite understand.  Even if it is on a different
> > partition, the path should still be the same should it not?
> > /var/spool should still work whether it is on /dev/hda2 or /dev/hda5 ?
> > 
> 
> What he is saying here, is that a 'mv' across multiple partitions, which 
> to the file-system, could be multiple devices, is not as simple as 
> moving a pointer.
> 
> For a 'mv' across partitions/disks, the file has to be 'copied' to the 
> new location and then 'removed' from the old location.  For a 'mv' 
> inside the same partition, the pointer in the file-system is simply 
> changed, and you're done.  Thus a 'mv' across partitions is not atomic, 
> and a 'mv' inside the partition is.

Not so much partitions as file systems, but otherwise you are right. A
filesystem can span multipple partitions and devices (think raid). A unix
file system really has to guarantee that from the user space view a rename
is an atomic operation. A rename can move a file from one location to
antoher within the file system. No such guarantee needs to be made across
filesystems. To give such a guarantee so would be unresonably hard (the
data would *have* to be copied) that is not required and usually not 
given.

Peter