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I have a 500 GB OneTouch4 drive connected to my Intel iMac. I have 60 GB of miscellaneous files on the drive in addition to the Time Machine backup files. The iMac has a 250 GB internal drive with an actual capacity of 232 GB and 160 GB unused space. Some time back I began getting messages from Time Machine that I had run out of space on the OneTouch and suggested that I get another drive. I turned off Time Machine.
My question is whether Time Machine saves the all updates of each file on the drive or just the latest version. Searches on various files shows that there is only one copy of each file on the OneTouch, so where did all the storage go?
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After making an initial full copy of your system's drive--file by file, not sector by sector--Time Machine scans your system hourly and copies the files changed since the last scan to the external drive. The copy is non-destructive: A file is not overwritten if the archive already has a copy of it. In effect, the old file is renamed before the new copy is written. A catalog tracks the location of every file in the archive, and the time at which file was appended to the archive.
See
this for more information. Hope it helps.
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I'm getting old so the brain is sometimes slow to assimilate information. If it's a non-destructive process, to me that means the old file is always retained. If that's so, why does a search on the drive only find one copy of a file. I tested it with FileMaker files, which, as we all know, get a new modified date every time they are opened. I have an FM file where I record every fuel fill for our 4 vehicles so it is opened quite frequently and changed. A search finds only one copy of a file with a name starting with "mileage". If the old file is renamed when backed up it should also begin with "mileage".
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I haven't used Time Machine yet, but I have read about it.
Check to see if the search feature is restricting the time window for the search. For example is it searching only in the files from yesterday or March 1, 2009 or something?
The way Time Machine works is that it periodically makes snapshots that mirror the exact state of the files and folders at certain points in time. When doing your search it makes sense that it would limit the search to one of these snapshots. This would avoid the problem of finding hundreds of identical files (one for each snapshot.)
Note that even though the same identical file may appear in 1000 Time Machine snapshots, if the file never changes, it doesn't take up 1000 times the space. Aside from a small amount of administrative overhead space, only one copy of the file is actually stored in the backup and many references are made to the original.
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deckeda wrote:
IIt does this with "hard links" which have the effect of making every file and folder appear to be originals, but they aren't. They only represent versions, and are really only complete files once restored back.
No, this is incorrect. Apple does use hard links, but they are in every way the original. There is no compromise.
With hard linking you now have two or more "originals" that are on equal footing to the filesystem, operating system, everything. Think of it this way. Every normal file on your computer is a hard linked file. You can make an additional hard link to refer to that same file under a different name (or the same name in a different folder which is what Time Machine does). The file system now has two ways to access that data. Delete one of the hard links (either one) and you have only one name (and path) to access the file. Delete the last hard link and the file is then deleted (or in old Unix-speak 'unlinked').
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I have not used TM much, but have had occasion to check it out on a client's computer. That computer had crashed, and she'd reinstalled the OS. I found her TM database in the Previous Systems directory, and to my delight, discovered that it is possible to dig into and find the actual files, without going through any sort of "restore" process via the Time Machine program itself... IIRC, it creates subdirectories by date, and you will find various versions of your files in those folders. For most users, however, I wouldn't recommend digging around in your TM directory like that!
Whatever the case, I think it unwise to use Spotlight to search for files in the TM directory. The best way to check how many previous versions of a particular file are in TM is using the TM interface itself. That's what it's for!
Lastly, check out
TimeMachineEditor for customizing TM's scheduled backups. It seems like most users would like to be able to edit TM's default schedule, and that program makes it easy as pie!
Good luck!
John
