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

Discussion in 'Mac Basics and Help' started by XPcentric, Nov 15, 2015.

  1. XPcentric, Nov 15, 2015
    Last edited: Nov 15, 2015

    XPcentric macrumors 6502

    Joined:
    Oct 16, 2008
    #1
    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)
     
  2. grahamperrin macrumors 601

    grahamperrin

    Joined:
    Jun 8, 2007
    #2
    How much disk space is occupied by that archive area?
     
  3. chrfr macrumors 603

    Joined:
    Jul 11, 2009
    #3
    If it's copying 10GB of new files, and archiving 10GB of existing files in your backup, that's 20GB.
     
  4. MacUser2525 macrumors 68000

    MacUser2525

    Joined:
    Mar 17, 2007
    Location:
    Canada
    #4
    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.
     
  5. XPcentric thread starter macrumors 6502

    Joined:
    Oct 16, 2008
    #5
    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.
     
  6. MacUser2525 macrumors 68000

    MacUser2525

    Joined:
    Mar 17, 2007
    Location:
    Canada
    #6
    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.
     
  7. grahamperrin macrumors 601

    grahamperrin

    Joined:
    Jun 8, 2007
    #7
    Which operating system?

    If not OS X 10.11.1 then at https://diigo.com/0xcp0 see the section about iosnoop.
     

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