Why Time Machine is not for me, and maybe not for you either...

[milo]

I second what these other guys said. That lengthy quote shows that you're wrong.

UNCHANGED files are not backed up again, they're just linked.

CHANGED files are backed up in their entirety, using the full amount of disk space again.

Those quotes make no mention of storing partial files, in fact it clearly states the opposite.

It's unfortunate that Time Machine's cleverness does not extend just a bit further. The smallest unit of data that Time Machine will backup is an individual file. That means that if you change one byte in a 10GB file, that entire 10GB file needs to be copied to the backup volume. Hard link can't help you here. There's no way to make a hard link to "9.99999GB of the old data, plus this one byte of new data."

 

[jolton]

Excellent you have just quoted an article that you have completely failed to understand.

What that quote is saying is that when Time Machine backs up your drive if a file has not changed then it will create a hard link to the original thus meaning the file will still show up in the Time Machine UI for that specific update of the backup. If it has changed then Time Machine will backup the entire file again in full.

Ah, okay. I guess I must have misunderstood. I stand corrected.

This sucks then. But I'll still use it.

 

[cmaier]

Personally, I prefer entire files to be backed up; it allows me to browse the time machine backup disk as if it is the full file system, and use any file just as if it was on my main drive. Storing diffs would make the backup useless for anything other than restoring. (Storing changed blocks and making the file still appear whole, ala zfs, would be cool, thoguh).

 

[saltyzoo]

Personally, I prefer entire files to be backed up; it allows me to browse the time machine backup disk as if it is the full file system, and use any file just as if it was on my main drive. Storing diffs would make the backup useless for anything other than restoring. (Storing changed blocks and making the file still appear whole, ala zfs, would be cool, thoguh).

That's why it works the way it does.

 

[CalBoy]

So the consensus of this 'focus' group p) is that Time Machine does indeed use a file's entire size storage size when even one minor edit occurs correct?

And am I also correct in assuming that we think that excluding large files from Time Machine and backing them up manually is the best way to go?

 

[saltyzoo]

So the consensus of this 'focus' group p) is that Time Machine does indeed use a file's entire size storage size when even one minor edit occurs correct?

And am I also correct in assuming that we think that excluding large files from Time Machine and backing them up manually is the best way to go?

That would depend on your use. How often you modify the file, how bothersome the performance hit would be while backing up, space requirements necessary, how critical it is for the file to be backed up, etc.

 

[CalBoy]

That would depend on your use. How often you modify the file, how bothersome the performance hit would be while backing up, space requirements necessary, how critical it is for the file to be backed up, etc.

Well naturally, but I was trying to refer to that previous poster who was upset that his over 1GB file would eat up his external.

 

[cmaier]

So the consensus of this 'focus' group p) is that Time Machine does indeed use a file's entire size storage size when even one minor edit occurs correct?

Absolutely. All copying is done at the file level. No way to do otherwise and still maintain the ability to see entire file trees w/o having to on-the-fly reconstruct them, at least until they switch to a new file system.

Note that the motivation to use many small, rather than single large, files has existed for awhile, due to spotlight, so other than a few special cases (VM files) and out-of-date actors (entourage), things shouldn't be too bad.

You would need the backup disk to be bigger than the drive you are backing up in any case, so it's just a question of how much bigger. (or of turning off backup to certain files - VM for sure, entourage maybe)

 

[milo]

I'd love to use this to back up my iTunes library, but it sounds like it may waste a ton of space, if changes to metadata require backing up entire files.

If I change things like year, genre, etc, isn't that changing the file? What about audiobooks, will the bookmark in the file keep causing the same file to get backed up redundantly? What about remembering the place in videos and movies? And what about star ratings, are those in the file or stored in the iTunes library?

 

[cowm007]

Don't know if you guys gets this, but Time Machine doesn't stop backing up till it's full and then stops. The idea is that, assuming you have a drive that matches your internal drive, you will at least have a backup of all your current files. Then, depending on how much extra space you have, it will be able to save various versions of each file and what not. It's not a CVS, it's a backup utility.

I've had my drive fill up already by making changes to iTunes TV shows tags. Time Machine is smart enough to delete the older backups to free up space and ensure that my latest files are all backed up.

If you need to ensure that all previous copies of a file are preserved, get yourself a versioning system. Time Machine just serves as a backup utility, with the added bonus that if space permits, older versions and deleted files will be preserved.