Carl Wilhelm Soderstrom writes:

> I got the files all copied over from the old backup server to the new backup
> server in record time by dd'ing the partition and sending it across the wire
> with netcat. (then writing it to the new partition on the other machine and
> using resize_reiserfs to take advantage of the new space).
> 
> unfortunately, the UID for backuppc changed between the old system and the
> new one; so I'm doing a chown on all the files.. which might be ~2.5 million
> when they're all hardlinked together, but are substantially more when you
> have to traverse all the trees. :(
> 
> now that I'm partway through the chown process I can't go back and just
> change the UID for backuppc (tho really it would be best to chown all the
> files and be up to the latest debian standards for UID).
> 
> for future reference, can anyone think of a faster way to chown several tens
> of millions of files that are all hardlinked together? if I chown all the
> files in the pools, that will also chown the files in the per-pc
> directories; and concievably I could then go through with a 'find -type d'
> to get all the directories in the per-pc files... but I don't know how much
> time that might save, since it would have to traverse all the directory
> indices anyway, then exec another command. also, there's a chance I could
> miss some files.
> 
> so I'm just letting it get on with a command like:
> 
> cd /var/lib/backuppc
> chown -R backuppc: .
> 
> this may take until tomorrow, unfortunately. :(

I don't have a better way.  I suspect the reason it is slow is
that each directory typically has widely-distributed inodes,
because of the hardlinking.  That means a program that works
through each file in each directory does lots of disk seeks.
It's likely the same issue that limits the overall performance
of BackupPC.

A possible enhancement for Roy Keene's BackupPC client project
is to sort files in inode order on the server when processing
each directory.

Craig


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