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Time Machine


Apple has added something they are calling Time Machine to the upcoming "Leopard" release of OSX.

My very first thought was that they've wrapped a gui front-end around filesystem versioning or snapshots. That would be the logical way to do this; otherwise you waste a tremendous amount of unnecessary space for backup:

(From http://www.macworld.com/2006/08/firstlooks/leotimemac/index.php):

How will Time Machine work for people who modify gigantic files on a regular basis? For example, consider a 1GB database file. If I make a tiny modification to that file, Time Machine writes out another 1GB file to record that change. As a result, drive space on my backup device could quickly disappear.

A while back, it was rumored that Apple might be working on ZFS for Leopard. Is that how they are doing this? Well, maybe, but others say "ZFS is not in the Leopard discussed at WWDC in any capacity"

Maybe they added versioning to HFS+?. It wouldn't seem all that hard to do given the metadata capabilities already present. Versioning itself isn't all that new; it goes back to DEC's TENEX and VMS filesystems. Even SCO implemented undelete with versioning. But no, the descriptions of Time Machine don't sound like versioning: they talk about having a separate drive for the backups. So that's probably not it.

So do they really duplicate data over and over again? That seems so unlikely. At the very least a simple version control diff method would cut down on that tremendously. But we don't yet know. Wikipedia's reference says:

It is unclear at this time whether Time Machine should be considered as a simple back-up utility or as a complete filesystem-level version control mechanism. Apple's website merely states that an API will be released so that third party developers can take advantage of Time Machine.

And that's where it stands for now.

If you want a great guide to learning about backing up your Mac, consider Joe Kissel's Take Control of Mac OS X Backups , a $15.00 PDF E-book that will teach you everything you need to know.

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© Anthony Lawrence

Sat Aug 12 16:24:40 2006: 2391   anonymous

Personally I don't like external harddrives for backup anyways. If you backup media is less reliable then the machine your backing up you've got problems and I don't think most external drives have very long lifespans.

Tend to get dropped, tend to overheat. That sort of thing.

But other then that Time Machine would probably be usefull. Not many backup mechanisms are going to have application-level support.

I think it's some sort of version control software. With Linux there are scemes to build a file system around something like CVS. For instance there is wdfs, which is webdav-based FUSE filesystem. With that you can combine Webdav + Apache + SVN to build a sort of distributed revision control system. The nice thing about it would be that your data would be accessable through a veriaty of clients. The downside is that it sounds very slow.

But there are other ones like that.

If it's a revision control system then how much space you'd end up using depends on how smart it is.. CVS for examples is a good compact one that has been around for ever, but it can't handle binary files very well. It'll just make entire copies of them. SVN on the other hand is suppose to handle that sort of thing much better. So you could definately end up with a situation were you end up having entire copies of something like a database file vs work documents that are mostly going to be zipped files of textual information.

People seem to like comparing Time Machine to Shadow Copy feature in Windows 2003 file sharing and Vista. Microsoft is kinda using Shadow copy as a feature bullet point of why you should want to buy Vista.

Now Shadow copy feature is definately a GUI front end on volume snapshots. At least in W2k3 a administrator has to setup dedicated space for it, schedule how many 'shadow copies' he'd like to make, how often to make them, and that sort of thing.

Of course Time machine may be a response to shadow copy, but Time machine would be a backup mechanism (seeing how it goes to a external volume) were shadow copy is more of a fancier undelete.

Wed Aug 16 17:37:27 2006: 2400   bruceg2004

I DUGG this article, in hopes of spurring some discussion on the possibility that Apple may include ZFS. ZFS certainly looks fantastic on paper, and I have not hear anything bad about it running on Solaris. If Apple where to put this in OS X Server, I would most likely purchase a copy. I have to solve some backup/restore issues, and having something like Time Machine and ZFS available to provide users with an easy to use versioning system would be great.

- Bruce

Thu Jun 7 16:40:18 2007: 3024   TonyLawrence

Looks now that ZFS will be in Leopard: (link)

So get ready to backup and reinstall :-)

Wed Jun 13 10:52:07 2007: 3030   TonyLawrence

Then you see it, now you don't:

(link dead, sorry)
says "no zfs"

Wed Nov 7 15:57:39 2007: 3236   TonyLawrence

So, Time Machine is pretty neat, more like Rsnapshot than anything else:


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