What capacity do I need for Time Machine

Discussion in 'Mac Basics and Help' started by novetan, Nov 2, 2016.

  1. novetan macrumors 6502

    Sep 3, 2010
    My com storage is 2TB. Do I only need to get a external 2TB hard disc for TM or the storage has to be more. If more, how much more?
  2. JohnDS macrumors 65816

    Oct 25, 2015
    Rule of thumb is that the Time Machine volume should be twice the size of the data it is backing up.
  3. adib macrumors regular


    Jun 11, 2010
    Another rule of thumb is that don't share the same partition with other data. I experienced a number of times that an improperly unmounted Time Machine drive developed filesystem errors beyond repairs (and had to reformat).

    Another is that you shouldn't depend Time Machine to archive things for you. Keep another drive for archival purposes (or at least another partition).
  4. Tomorrow macrumors 604


    Mar 2, 2008
    Always a day away
    It depends on how full the 2 Tb drive is, and how frequently you update or change files on it. 4 Tb would be more than enough for most people. My old iMac had a 1 Tb drive and I used a 1.5 Tb drive for Time Machine. Over the course of several years, I only used about 800 Gb of the TM drive.
  5. Hustler1337 macrumors 68000


    Dec 23, 2010
    London, UK
    There's a comprehensive guide on Time Machine by James Pond and it's the best resource on Time Machine out there. He states "A general "rule of thumb" is, to keep a reasonable "depth" of backups, Time Machine needs 2 to 4 times as much space as the data it's backing-up (not necessarily the entire size of your internal HD)."

    Would highly recommend checking it out: http://pondini.org/TM/1.html
  6. novetan thread starter macrumors 6502

    Sep 3, 2010
    Tks for the links. I hv gone thru it and very informative.
  7. KALLT, Nov 4, 2016
    Last edited: Nov 4, 2016

    KALLT macrumors 601

    Sep 23, 2008
    Technically, you only need as much space as you are trying to back up or as much as your main drive can hold. Your system has caches worth gigabytes and other things that are never backed up. Thus a 2 TB drive would be enough to make a backup for a 2 TB system. The only reason why you should use more is to make use of snapshots. Depending on your disk usage, filling up the remaining space can take weeks or months or even just an hour if you make very big changes.

    I only use a ratio of 1:1.2 of my drive’s size, as my main disk is never filled anyway and I don’t really need the snapshots, aside from a buffer for system upgrades. I still have two months worth of snapshots.

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