Daniel Eran Dilger
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Ten Myths of Leopard: 6 Time Machine Eats Hard Drives!

Ten Myths of Leopard: 6 Time Machine Eats Hard Drives!
Daniel Eran Dilger

Myth 6 in the Ten Myths of Leopard.

Ten Myths of Leopard: 1 Graphics Must Be Slow!
Ten Myths of Leopard: 2 It’s Only a Service Pack!
Ten Myths of Leopard: 3 Nothing New for Developers!
Ten Myths of Leopard: 4 Java 6 Abandonment!
Ten Myths of Leopard: 5 “Back To My Mac” Security Panic!
Ten Myths of Leopard: 6 Time Machine Eats Hard Drives!

Ten Myths of Apple iPhone
Ten Myths of the Apple TV


Myth 6: Leopard’s Time Machine is Just Like Windows And Eats Hard Drives. I’ve already deflated the Time Machine Is Like Something In Windows Myth. The short version: try to do a system wide search of your desktop environment from two weeks ago. Is Shadow Copy any help? Windows XP and Vista can’t even search your current files rapidly, let alone search the archives they don’t really keep on a regular basis.

Next, try to restore a photo from your album database. Or a contact from your address book. In Windows, you’ll have to restore an entire database, then plug it in to see if you can find what you were looking for. Time Machine lets you search collections, something no other backup system makes even remotely easy.

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Backups Ate My Hard Drive.
The obvious other complaint leveled against Time Machine is that backing up all your files… takes up hard drive space. Rob Mead, who earlier complained about the supposed security problem in Back to My Mac, worries that users will have to start over with new hard drives when they fill theirs up. Oh the troubles of paradise. Imagine having so much of your data backed up that you need stacks of hard drives just to feed Time Machine’s addiction.

Back in reality-land: if you look at how Time Machine works, it was designed to rapidly chow up space to keep hourly backups as long as you keep your Time Machine backup drive plugged in. However, every day it drops the hourly snapshots of the previous day to keep just one good record set per day. That means Time Machine will rapidly eat up hard drive space, then level off after the first 24 hours as it starts shuffling less important archives out to save new sessions.

It similarly eats up a week’s worth of daily backups, but then slows down by dumping daily backups as they become older than a week. Time Machine also intelligently thins out older copies of files, so you don’t end up with too much junk. The more disk space you give it, the less thinning does. The option to “Warn when old backups are deleted” is on by default.

This design allows you to choose what kind of backups you want to perform, without having to become an expert in data archival rules and scheduling. Word to the wise: nobody ever died from having too many backups. With Time Machine, you end up with a balanced set of backups without having to think about the details. That means your backups will actually get done, and will be available when you actually need them.

Road to Mac OS X Leopard: Time Machine – AppleInsider

What do you think? I really like to hear from readers. Comment in the Forum or email me with your ideas.

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  • larryv

    It certainly is silly to think that Time Machine will gobble up your hard drives one after another, but from what I understand, it does it in a way even more clever than you describe here.

    Unless I’m mistaken, Time Machine doesn’t really chow up space at all, and it doesn’t take 24 hours to “level off”—it does so after the first backup! When Time Machine first begins working with a particular external drive, it makes a complete backup of the entire system. Then, every hour, it only copies those files which have changed since the the last hourly backup. However, it maintains a “complete” record for each hourly backup by creating hard links to data that has not changed.

    For example, after 6 hourly backups, a file that does not change very often (e.g., /System/Library/Filesystems/zfs.fs) will have 6 hard links associated with it, while its data will only take up 160 KB, not 960 KB. On the other hand, a 1 MB file that has changed more frequently than ever hour (a report, say) will take up 6 MB.

    A more technical description can be found here:
    http://arstechnica.com/reviews/os/mac-os-x-10-5.ars/14

  • http://web.mac.com/lowededwookie lowededwookie

    Who are these muppets that spew this bollocks?

    Clearly they have no idea about backups.

    When I was doing onsite support I was in charge of backups. I would have to do a daily backup which was on a set of 5 tapes on a two week rotation. Then there was a monthly tape which was on a 12 monthly rotation. Finally there was one large one that was a yearly backup which was never rotated and had to be kept for 7 years.

    The fact that Time Machine does the same thing but on a single drive is both time saving and fire and forget but reliable. There were times when I forgot to do a backup or something went wrong with the tape or system.

    Very little can go wrong with Time Machine because the routine is hourly, daily, weekly, monthly. How is this difficult to understand?

    My only gripe would be that you can’t set another drive for monthly backups.

  • Bobson

    I’m surprised you didn’t mention what I think is the best space-saving feature of Time Machine: hard links. Have a huge number of copies of your entire drive… and yet have it take up a minimal amount of actual space, because not many files change.

    If I leave my computer sitting untouched all day while I’m out of the house, it still generates its hourly backups, but it won’t ever fill up the drive. Just one less way it can “eat up” my drive!

  • elppa

    Windows Vista search can be quite snappy.

    I have yet to have any success searching for anything in XP though.

  • larryv

    I, likewise, have never successfully found anything using Windows XP search. Ever.

  • lmasanti

    The one thing I think it is missing is the ability to do a “full off-device backup”, likt to dvd or other disk, to be put on other location.

  • Bobson

    lmasanti – that’s easy. Just go into your Time Machine drive, pick the folder for the backup you wish to off-site, and drag/burn it as appropriate. Alternatively, plug in a new drive and set it as your time machine drive for one backup, then switch back and take that off site.