The macosxhints Forums - TimeMachine est backup size larger than whole drive!

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- - TimeMachine est backup size larger than whole drive! (http://hintsforums.macworld.com/showthread.php?t=156087)

If you modify the file in the next hour, then you will, most likely, re-write the entire file on your system disk. And then TM will back it up. So we're still on parity here. The difference is that TM didn't overwrite the old file.

If you don't modify it: TM does NOT make a copy.

And, TM copy writes to the TM volume, not to the boot drive.
Outside of your initial TM backup (which can take a significant amount of time to complete), normal TM activity is not too involved, compared to the normal read/writes that your system does outside of TM.

OK...both your replies are very illuminating...

So, even the major backups will most likely be lighter on the hardware than the initial, unless I do more work, create more files and make more changes equalling to more space and file size than the original..

maybe the first TM back up is a huge gulp, thereafter...little sips?

a

Quote:

Originally Posted by acme (Post 696697)

maybe the first TM back up is a huge gulp, thereafter...little sips?

That pretty much sums it up.

Quote:

Originally Posted by ganbustein (Post 696650)

Then it asks those three questions.

What, no creaky bridge here?

Quote:

Originally Posted by acme (Post 696690)

sorry to bump this question, but I have a concern whether Time Machine use causes an increase in wear on the drives involved in making the constant backups.

...but I've I'm working hot and heavy with many photoshop files, or editing video, I can see it running into serious amounts of data and therefore more work being demanded of those drives.

Wear & tear on a spinning drive is of minimal concern until it's excessive (like defragmenting)

Extensive video editing that changes the original files (check the modified dates) will fill up your backup drive in record time - in this case good practice is get a good external*, put the video files on it (and redirect the editor's scratch space there) and exclude this drive from TM. You typically don't need a backup of video workfiles as you should still have the originals in the camera.

* full-size drive, FW800 or Thunderbolt case. A pocket USB drive would be a very poor choice. A 15,000 rpm drive with eSATA or Tunderbolt would be excellent.

Quote:

Originally Posted by ganbustein (Post 696650)

As of 10.7.2, every time you do a TM backup to a local disk, Time Machine makes sure there's a current version of a file named tmbootpicker.efi at the root level of the backup, and blesses that as the startup file.

As nearly as I can figure out, tmbootpicker.efi has the same code found in the firmware of modern Macintoshes that handles the ⌘R combination at startup. What the code does is look for any "Recovery HD" partition (I would presume the latest if given a choice) or, if not finding any, downloads one from Apple into RAM.

...snip...

Thus, the real significance of the TM volume being bootable is that it brings the benefits of Lion Internet Recovery to users whose Macs are new enough to run Lion (or MtLion) but not new enough to have LIR in their firmware. It would behoove users to arrange to also have at least one copy of Recovery HD always available, ideally on the TM volume itself, to forestall a 650MB download.

I want to correct an egregious error in what I posted.

In addition to creating the tmbootpicker.efi file, Time machine also creates a folder Backups.backupdb/.RecoverySets/0/com.apple.recovery.boot on the backup disk, and populates it with the same data found in the com.apple.recovery.boot folder found at the top level of the recovery partition. In particular, both folders contain BaseSystem.dmg, which is what you actually boot from when you boot into recovery mode.

Thus, a Time Machine backup volume is bootable and completely self-contained, not requiring the existence of a "Recovery HD" partition anywhere else, nor on having Lion Internet Recovery in firmware. Booting into it has the same effect as booting into a "Recovery HD" partition without actually needing one.

All of this applies when backing up to a directly-connected local disk. I don't know if TM puts this same information on a Time Capsule backup, nor if it's even possible to boot off a Time Capsule

I had searched my Time Machine backup volume for an equivalent to Recovery HD, and when I couldn't find one on the volume assumed that tmbootpicker.efi was pulling the information from elsewhere. Only a "real" Recovery HD was large enough to contain all the code it was using. Perhaps what threw me was that at the time I didn't know what the innards of Recovery HD looked like, and must have dismissed com.apple.recovery.boot as being too small. (It's 468MB, compared to 650MB for Recovery HD.) Since then, I've explored inside Recovery HD, and see that it is in fact complete, with most of the size difference being just room reserved for expansion.

Sorry for posting inaccurate information.