Time Machine backing up to a USB Flash drive?

Discussion in 'Buying Tips and Advice' started by RedTomato, Sep 14, 2008.

  1. RedTomato macrumors 601

    RedTomato

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    .. London ..
    #1
    Hello,

    I just saw 16GB USB flash drives on sale for £25, which isn't much. That makes me wonder if it's becoming feasible to use Time Machine to back up to a USB flash drive?

    Obviously you can't back up the whole system, but 16 GB would be enough to cover the documents folder of a lot of people. 64GB flash drives are out now, and that's nearly enough for a whole Macbook Air.

    An advantage is it would use less battery power than backing up to a 2.5'' portable drive.

    One issue is wearing out the write cycles of the flash drive, but they are so sturdy nowadays, and also TM doesn't cycle memory that much - only writing new stuff each hour (while plugged in) and erasing old stuff when the drive is full.

    Interesting? Do people already do this? A google search found nothing.
     
  2. DMC-12 macrumors 6502

    DMC-12

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    #2
    Doesn't the TM backup drive have to be at least the size of your Mac's hard drive?
     
  3. Eidorian macrumors Penryn

    Eidorian

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    #3
    It'll work just fine. Just exclude what you don't want backed up to the flash drive to save on space.
     
  4. kurzz macrumors 6502

    kurzz

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    #4
    Not unless your hard drive is entirely filled up. Time Machine only backs up what you currently have on the HD..it doesn't backup the empty space!
     
  5. DMC-12 macrumors 6502

    DMC-12

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    #5
    OK, this makes sense. Good to know.
     
  6. Shagrat macrumors 6502a

    Shagrat

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    #6
    Sounds like a cool idea! Good thinking. Will try it out myself!
     
  7. RedTomato thread starter macrumors 601

    RedTomato

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    #7
    It's a shame you can't set TM options on a disk by disk basis - I'd like to set up something like this:

    - working documents folders backed up via TM to a 16GB USB stick while I'm out or travelling.

    - At home or the office, have TM back up the entire HD to my 1TB Time Capsules.
     
  8. kurzz macrumors 6502

    kurzz

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    #8
    Also keep in mind, however, that Time Machine keeps multiple copies of your backup, hourly, daily, weekly, monthly, etc. So, the larger the space available to it, the "further back in time" you can go.
     
  9. simonsimon macrumors newbie

    Joined:
    Oct 6, 2008
    #9
    I've been trying to get Time Machine to back up just one folder to a 4GB usb flash drive.

    I've excluded everything except for this folder (at the top level on my hard disk) including invisible files and folders. There's only about 500mb of stuff in the folder.
    However, when it tries to do the backup I get a message saying that there's not enough space, that it needs 10gb. I tried again with just an excel document (24kb) in the folder, same problem! When I do (exactly) this to an external hard disk with 12gb free, no worries, it backs up, and the backup folder on the hard disk only takes up 88kb.

    Does anyone know how to make this work? Why does Time Machine want such a huge amount of free space for a small folder? Even with the 500mb folder it wants 20x the space.
     
  10. RedTomato thread starter macrumors 601

    RedTomato

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    #10
    I've been doing some poking around, and I suspect having that folder at the top level might make a difference. Try backing up a single folder on your desktop or just your documents folder, or a single folder in your home, and see if that makes a difference.
     
  11. rouquin macrumors newbie

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    #11
    Actually, this is probably a case of you could, but should'nt.

    USB memory sticks have a limited number of read and write operations before they fail, whilst this is not a problem for moving data around, or carrying it with you, it does become an issue if there are lots of updates occurring, i.e. something like time machine accessing the stick every hour and doing lots of read and write operations.

    It might be fine for several months (we are talking 10's of thousands of reads / writes after all), but I would not want to trust one as being my only backup.
     
  12. Littleodie914 macrumors 68000

    Littleodie914

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    #12
    It should work, as many other posters have mentioned, but one thing I thought I would add is the serious speed difference between a flash drive and an external HD. Flash drives are much slower, both for reading and writing, than traditional "platter" drives.

    Flash storage is getting faster, but you'll still see huge differences (close to 10x faster on a traditional drive). :eek:
     
  13. RedTomato thread starter macrumors 601

    RedTomato

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    #13
    Bzzzz. Completely wrong. Time Machine doesn't do lots of reads and writes on a USB stick or the backup drive. It only writes what's new since the last backup. Which is usually not much.

    And while I'm not completely clear how it knows what to back up, I think it works with the OS to maintain a list of what files have been touched, then when a back-up is done, that list (which is possibly stored on the host drive) is cleared.

    There are a couple of other ways it might know what needs to be backed up, but none of them involve having to scan through every file on the USB stick / backup drive.
     
  14. rouquin macrumors newbie

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    #14
    I'm sure that your right and time machine is very clever in keeping track of the changes and minimising the backup device access.

    Nonetheless, I would not trust a USB stick as a long term backup device. I tend to change files throughout the day as I work, so the work that time machine does it very real. Even if there have been no changes, time machine will still access the backup device and write some information (use the backup now feature a couple of times when nothing else is going on and no files have been changed and watch the activity monitor). Those reads and writes soon clock up over a few months.

    Please note that I am using phrases like 'long term' and 'months', duty cycles that do not trouble most hard disks too much (yeah I know there are always going to be some duff ones).

    Would you trust a USB stick with your time machine backup?
     
  15. simonsimon macrumors newbie

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    Oct 6, 2008
    #15
    I have an external hard disk at home that I back up my macbook to every time I go home (every few days), and I need the USB backup for those in between times. So system, music, photos, all the big stuff is all backed up there. I just need two or three days of work backed up for the in-between.

    If it only lasts a 6 months, that doesn't matter. It's better than carrying around a hard disk.

    Interestingly when I choose a folder on one of my smaller external disks (only 120gb, my internal is 320gb) then it says I only need 5gb free. Not 10gb.

    Does time machine decide how big the disk needs to be based on your hard drive capacity, rather than actual size of data you want to back up?
     
  16. Diagoras, Oct 28, 2018
    Last edited: Oct 28, 2018

    Diagoras macrumors newbie

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    Nov 16, 2013
    #16
    FWIW I tried backing up the hard drive of my late 2012 MacBook Pro with Time Machine using a Kingston 64 GB DT SWIVL. The laptop's 120 GB hard drive contained about 40 GB of data. It was taking so long that I thought something was wrong, tried to eject it and eventually had to force eject the USB drive. I reformatted the USB drive to erase anything on it and started Time Machine again. After 22 hours, by which time Time Machine had processed 26 GB, the backing up stopped. Now when I insert it into the Mac the icon shows under "Devices" and on Desktop for 30 seconds and then apparently self ejects. Kingston reps aren't all that familiar with Time Machine but using Apple's instructions they suspect that a thumb drive may not meet Apple's specs.
     
  17. RedTomato thread starter macrumors 601

    RedTomato

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    #17
    You’re quoting something I wrote TEN years ago?

    :)
     
  18. Diagoras macrumors newbie

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    Nov 16, 2013
    #18
    Why so touchy? I'm just giving my own experience. My suspicion is that either the Kingston flash drive is defective or force ejecting it while Time Machine was running may have damaged it. Now, despite reformatting it for my Samsung QLED TV it won't even record.
     
  19. RedTomato thread starter macrumors 601

    RedTomato

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    #19
    Ah don't worry about it - it was an amused comment :)

    On your point, I think you're right, flash drives don't cope well with masses of small constantly updated files.

    I tried keeping a Photos library (about 10k images & associated database ) on a good quality 200GB SD card. Didn't work well. Photos kept complaining that its library was corrupt and having to rebuild it.

    I also tried keeping a large team Dropbox folder (about 50GB, lots of changes and updates) on an SD card. Sometimes it ran well, but every few months something would get stuck and the solution was to delete and re-download the Dropbox folder.

    Time Machine will suffer much the same issues, so no, don't use USB flash drives for Time Machine.
     
  20. ignatius345 macrumors 68020

    Joined:
    Aug 20, 2015
    #20
    If you're dealing with 16GB or less of files, why not just use Dropbox or Google Drive or iCloud Drive?

    [edit: good lord, this is a ten-year old thread someone resurrected for some reason. No wonder nothing about the problem or the "solution" seems to make sense in 2018]
     

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19 September 14, 2008