Monday, December 21, 2009

Freeing up Time Capsule space – and documentation for Time Machine and Time Capsule

[See Update for the bottom line -- my original impressions were a bit off]

I bought my 500 GB Time Capsule a few weeks before Apple upgraded performance and doubled drive capacity (they probably fixed the original’s flaky power supply too).


In any case adding a new iMac means the TC is blinking amber – it’s short of space. I could replace the 500 with a 1.5 or 2.0 TB Western Digital Green Power drive but the upgrade looks like a pain and it would void my original warrantee (which I might need thanks to that flaky power supply).

In reality 500GB is enough for what I truly need to backup – at this time*. I just need to free up space by excluding the System and Application folders from backup. (You can’t specify which folders to include, only which to exclude.)

This being the modern era it’s quite a chore to find Apple documentation on the Time Capsule (Google is less help than one would expect). Here’s the current list I have:

Specific references on removing backups and freeing up TC storage:

  • Erase and reformat an Apple Time Capsule- Dave Taylor: Use AirPort Time Capsule UI to reformat the drive. It works, but see Update for a 10.5 bug that might impact restarting your backups. It means all backups need to be redone, see update for removing just one machine backup.
  • Removing backups from Apple’s Time Machine: This is more intriguing than I first thought, but it's somewhat different from what I've read elsewhere. Proceed with caution: I'd try other methods first. Note that TM doesn't always free up space immediately - the sparse bundle doesn't auto-compact. This article and others suggest use the "hdiutil compact" command to force sparse bundle compression.
  • Removing backups by deleting the sparse image bunde: Joe Kissell, author of the superb Take Control of Mac OS X Backups wrote to me about this (see Update). I purchased the eBook and he responded very quickly to this specific question.

Some additional non-Apple references …

Among other tidbits it’s useful to know that …

  • When using Time Machine, the little “gear” icon in the Finder view is not what you think it is. It’s a control element for the Time Capsule interface. Nobody has ever figured this out on their own. (See the FAQ for how to restore this if you don’t see it. World’s most inane UI decision.
  • If you control-click the Time Machine Dock icon (better make sure you add one to your dock!) you can “browser other backups”.
  • For ease of cleaning out Time Machine backups, it’s best to use an external drive that you can reformat. If you want an external drive to do more that TM, you should partition it.
  • If you back up more than one machine to a TM drive (which is what Time Capsule does) you should ideally have a separate partition for each machine. Otherwise the backup pruning algorithms have suboptimal behavior (this is what I’m seeing with my Time Capsule). The user-compiled FA
  • There’s a free dashboard app that shows Time Machine messages.
  • If you want to use the TC as a file share, one good approach is to create a disk image on the TC that will handle your file share files - keeps them separate from the backup sparse bundle images.

The best reference is the user-compiled FAQ.

* I have a completely separate redundant Retrospect Professional backup system with larger capacity. Yes, I have two automated backup systems, one of which has offsite rotation. Yes, I’m berserk on backups. Incidentally, the more I study this, the more I think it will make more sense to add an external 2TB drive to my primary iMac and network server than to revise my Time Capsule.

Update 1/1/2010: I find a bug in TM that caused a restore to fail. There's a workaround.

Update 1/22/2010: I finally did the clean-up and restore, and discovered a 10.5 bug that hits when you erase a Time Capsule.

Update 1/25/2010: Next time I'll remove just the problematic sparse image per the advice of Joe Kissell, author of an eBook I bought: Take Control of Mac OS X Backups

First, in the Time Machine preference pane for the Mac in question, click Select Disk and then click Stop Backing Up.

Next, if you back up to a Time Capsule or other network drive (as I'm guessing you do), you must mount that volume in the Finder. For example, select your Time Capsule in the Finder sidebar, and if its volume doesn't appear automatically in a few seconds, click Connect As and enter your credentials. On that volume you'll see a disk image for each computer you back up. Drag the one in question to the Trash and click Delete.

Or, if you back up to a locally connected drive, instead of disk images at the top level of the drive, you'll see a top-level folder called Backups.backupdb, and inside that should be a folder for each Mac. Drag the appropriate Mac's folder to the Trash and empty the Trash. Note that emptying the Trash could take a *very* long time!

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