External HDD and time machine question.

Discussion in 'Mac Basics and Help' started by hodgey1989, Jun 4, 2009.

  1. hodgey1989 macrumors member

    Jan 22, 2008
    Im looking to get an external hard drive for the use of time machine when i get my MBP (after wwdc). Ill be getting the one with the 320gb hard drive.

    My question is would a 500gb external HDD be ok or would 1TB be better?

    I ask this as i dont know how time machine works as to how it stores data, does it store everything you ever have on your computer, so if i filled the HDD 3 times it would be about 1TB.

    Hope you understand my babble lol.

    Thanks for any help :)
  2. patrick0brien macrumors 68040


    Oct 24, 2002
    The West Loop

    You're more informed than I think you give yourself credit for.

    Yes, your backup drive should always be at least the same size as the source volume (I say it that way as if you had more than one source drive, Time Machine can back them all up).

    With an incremental backup utility like Time Machine, the backup drive should be as big as you can afford. This way, you can have more history available to you.

    Case and point, I have 2 1TB drives in my MP, about 500Gb of actual data. These drives are Time Machine'd on a Drobo with 4 1TB drives - this yields about 2.75TB of actual backup space (the Drobo keeps a drive for RAID redundancy). So I figure I can get almost 6 months of backups in there before Time Machine will start to overwrite the old stuff.

    Equation used: 2.75TB*1024=2816 actual GB useable. 2816/500=5.632 months

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