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Why does rsync writes to disk double the amount I backup ?

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XPcentric

macrumors 6502
Original poster
Oct 16, 2008
271
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I'm using rsync to backup and I use more options with it, including the option to archive.
I backed up about 10GB, the destination show to be exactly that, but Activity Monitor shows it has written 20GB. (not including previous system writes, suppose I do back up immediately after I open the Macbook)
 
Last edited:
XPcentric said:
I'm using rsync to backup and I use more options with it, including the option to archive.
I backed up about 10GB, the destination show to be exactly that, but Activity Monitor shows it has written 20GB. (not including previous system writes, suppose I do back up immediately after I open the Macbook)
Click to expand...
If it's copying 10GB of new files, and archiving 10GB of existing files in your backup, that's 20GB.
 
chrfr said:
If it's copying 10GB of new files, and archiving 10GB of existing files in your backup, that's 20GB.
Click to expand...

If you are referring to the -a or --archive switch then that is not what it does. I use it all the time and I have never seen a doubling of the data involved. OP post the command you use so we can try to figure out what is happening.
 
Code: 
rsync --archive --one-file-system --sparse --xattrs  /Users/user    /Volumes/untitled

Thanks for all answers. I hope I was not misunderstood.

Source is 10GB / Users/user
Destination back up is also 10GB (not an archive) /Volumes/untitled
The option archive I talk about is "rsync --archive" which as I understood keeps file attributes, symbolic links and possible makes the transfer faster when done over internet.

But. Activity monitor shows a cumulative of 20GB written. Activity monitor does not say to which disk it has written that much, its just a total. My guess is that files that are supposed to be backed up are first archived in a temporary directory on my local disk, and then they are transferred to the external Volume ?
If that is true, maybe I'll find an alternative to using --archive option.
 
XPcentric said:
Code: 
rsync --archive --one-file-system --sparse --xattrs  /Users/user    /Volumes/untitled

Thanks for all answers. I hope I was not misunderstood.

Source is 10GB / Users/user
Destination back up is also 10GB (not an archive) /Volumes/untitled
The option archive I talk about is "rsync --archive" which as I understood keeps file attributes, symbolic links and possible makes the transfer faster when done over internet.

But. Activity monitor shows a cumulative of 20GB written. Activity monitor does not say to which disk it has written that much, its just a total. My guess is that files that are supposed to be backed up are first archived in a temporary directory on my local disk, and then they are transferred to the external Volume ?
If that is true, maybe I'll find an alternative to using --archive option.
Click to expand...

That is not how it works add a -v in there and watch the output it gives you on the command line as it executes. You will see as I do all the time it processes one item at a time. Comparing the source to the destination then copying the changes if any between them. No clue on your activity monitor observations I have never even thought to look there while syncing but if your files end up the same on both ends of the copy I would think it is not much to worry about.
 
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