time machine


My information about using multiple Time Machine drives remains surprisingly popular, even 4 years after posting it. I missed this one in the massive list of features, but Apple appears to have added more robust support for multiple drives in Mountain Lion!

Thanks to Macworld for highlighting it, in an interesting list of Mountain Lion system changes.

I’ve been wondering, on and off for the last few months, why I persisted in nightly SuperDuper! backups in addition to Time Machine. Well now I know :)

In the middle of my last post I mentioned that I may have just screwed my USB ports. I had. This is a real problem when USB is the only input device – even my bluetooth keyboard wasn’t working! Thankfully I have just booted from the SuperDuper backup and am trying to restore all of the kext in the system folder, according to the package list that’s what the installer changed.

Even if this doesn’t work though, and I have to restore from backup, I at least have something I was able to use instead of being left with a brick requiring 2-3hrs of system restoration. Note to self though: when booting from the SuperDuper backup, don’t leave the Time Machine drive plugged in. TM just tried to do a backup which really wouldn’t end well ;)

I knew it was a good idea to keep these bootable backups going, I’d just forgotten why. As annoying as this will be it’s good to remind yourself now and then what the value of multiple backup strategies is. Even if it results in being so worried you’re up until 1am trying to fix it.

OS X Migration Assistant via network cable sucks. Even if it’s gigabit.

The new mini has arrived, and I decided to see if gigabit would be faster than my USB 5200rpm Time Machine drive for restoring a 40gb profile via the Migration Assistant. It was slooooow. I didn’t want to waste time setting up Time Machine, and I misread the free space on it, so after all that migration fun with the new backup drives I just said “bugger it” and wiped the Time Machine drive. The new initial backup is taking forever, so to be honest the network migration probably wound up around the same speed as direct TM restore would’ve been.

I know, I know… wiping backups is insane and stupid. I still have the second drive offsite with the old backups on it, but really I don’t think I care about historical backups that much. Just the protection of data. I might use the second drive as an experiment, see how TM handles backing up a new system with the same computer name (if it dies I’ll just wipe that one too).

 
On a lighter note, the new mini is suitably fast in the graphics department. I was totally delusional thinking it was anywhere near the speed of my desktop card (ATI x1950) but for the games I’ve been playing recently it seems fine. After looking at benchmarks, I certainly wasn’t expecting to play City of Heroes in full 1920×1200 resolution so that was a nice surprise :)

Now, on to formatting the old mini as a clean TV machine :D

Something I noticed very quickly last night after migrating my Time Machine partition was the drive speed. If you have ever wondered why Time Machine sometimes takes forever on the “preparing backup” stage you’ll likely find this message in your console:

Node requires deep traversal:/ reason:kFSEDBEventFlagMustScanSubDirs|kFSEDBEventFlagReasonEventDBUntrustable|

In english, that means the backup cache (FSEvents) is out of sync (it’s the fancy background process that tracks drive activity and makes Time Machine so fast). “Deep Traversal” means that your entire drive must be scanned and compared to the Time Machine drive before the current backup can proceed. I regularly see this when rotating my backup drives, but not always.

On my old backup drives this takes a grand total of 9 minutes. After pointing Time Machine at the copy of it’s data on my new drive however, it took 33 minutes. The question is, should I care? Subsequent incremental backups went at their usual pace (4 seconds to backup 600kb and delete a backup from 24hrs ago).

This drive is going to sit (eventually) in a place that I don’t notice it except on Friday morning when I unplug it to be rotated. It’s not like my mac seems to notice the difference, USB drives don’t putting any noticeable load on my CPU. If it takes 1 minute or 1 hour it isn’t likely to bother me either way unless the mac goes to sleep in the middle and it doesn’t finish the backup.

Considering the benefits I get (no noise, drastically reduced power usage, only 1 cable instead of 3) I think I can live with this minor flaw.

I bought a 250gb Seagate FreeAgent Go last year for transferring files around, and was absolutely amazed at the size and weight. After using it for a while I have decided that these drives will make a perfect backup solution; like most 2.5″ external drives it is impossible to know it’s active without looking at the glowing lights on top. This is in stark comparison to the drives I’m using now (see my most popular post ever for those details).

Take another look at my old desk setup. By the time I posted that I had already moved the big clunky backup drive off the desk and into a cupboard (via a very long FireWire cable) because the noise was so annoying in an otherwise fairly quiet room. I originally bought those drives because I wanted something cheap and user-servicable for the eventual day that the drive fills up. They definitely filled that need but at the same time you definitely get what you pay for.

The FreeAgent Go drives may be a little more expensive than the build-it-yourself models, but as well as being whisper-quiet they only need a single USB connector and it turns out Time Machine backups use even less space than I thought. Thanks to my rotation policy Time Machine’s weekly backups are spread across two drives – so with 2 instead of 4 per month on each drive I can only assume that the speed at which my backups are growing is halved. In the 4 months since I purchased the drives I have only created 85gb of backups (aided by the exclusion of my download and VM image folders). Who needs to worry about filling a 320gb drive at that rate?

It quickly became clear to me that I could use my existing FreeAgent drive for backups; 250gb is obviously plenty of room. I needed a second 250gb to continue my weekly rotation and then a new drive to store the data from my old 250. Prices have dropped so much in the last 4 months that the 320s are now going for the price of my first 250 so I went for a blue 320 (to help differentiate them). I had to lose a few USB devices but they’re all happily plugged in to my Mac while I do the migration:
multipass
(Compare that to the old desk to get an idea of how much better my desk looks. And yes, that’s one of the free Apple stickers on my old storage drive :)).

The first problem came when I was partitioning the new general storage drive. I have a pretty weird setup with 4 partitions; a 7 and 15gb for work, 60gb for the bootable backup and what’s left goes to general storage. Unfortunately, Disk Utility doesn’t like to play ball with partitions smaller than what will fit on the pretty little graph – it just never seems to get it right. This caused me a few headaches because even at 1920×1200 the smallest I could make a partition on the graph was 12gb and I need that 4th partition to be 7gb for a reason.

My solution, of course, was both crazy and brilliant at the same time:
vertical fun
I love my 24″ Dell monitor (one of the originals, with 5 inputs and a swivel desk mount). I haven’t used the vertical rotation in a while, it’s always easy to forget just how wide these monitors are :)

Once all that was done, I had to think about migrating my Time Machine backup. I wasn’t totally concerned about wiping the wrong drive (having an offsite backup relieves so much stress from this process) but it would still be annoying so I did a bit of research on migrating Time Machine drives. I’m not the first one to do this of course – and as any experienced OS X hacker would know, the best solution is using Disk Utility’s copy disk option. I have used DU’s restore feature before, but never read the fine print that said it could be used to duplicate partitions :)

I ran the restore process on my general storage partitions first; I needed to migrate the data to the new drive anyway, and if something went wrong I wouldn’t lose anything critical. After I was satisfied I began the big migration… DU reported nearly 1.1 million files on the TM drive so I was very glad to be doing a fast block copy with a full verification pass. No wonder people trying to use file-based copy methods have so many problems!

I hope this post is useful to someone (my last Time Machine post certainly has been). In the meantime, USB transfers apparently don’t take much CPU so I’ve been using my computer as normal while waiting for the copy to finish. This meant chaining a few USB hubs together – my USB Device Tree looks like an actual tree now :D
usbtree

Specifically TM users who have an iPhone or iPod touch. Right now, your iTunes device backups haven’t been backed up. I discovered this while restoring something from Application Support last week, and suddenly realised the MobileSync folder was missing!

I put it on my to-blog list but have been kinda busy; luckily it turns out Apple were already working on a fix :)

  • Time Machine can now back up iPhone backups that are on your Mac, as well as other items in (~/Library/Application Support).

In other words, upgrade. Upgrade now.

You’ll have to be an old school gamer to get that one.

The SuperDuper backup worked as advertised, but I’m an idiot; if you don’t want boring details you can skip the rest of the post because what happened is I killed my Time Machine partition.


So, why am I an idiot. I decided that instead of simply restoring, I’d bring the laptop to work and attempt to fix it; mount it on the spare mac we use for testing and either delete cache files or reinstall the security update. Both failed, so I copied SuperDuper to the mac and proceeded to restore.

Everything booted and I was really really happy… until I looked at the cables and realised I was completely screwed.

You see, my external hard drive has 2 firewire ports (I’m sure you can see where this is going) presumably so you can daisy-chain devices. That’s what I was doing because the mac only had one FireWire port, but I forgot to unmount the drive from the mac that did the restore before booting the laptop – which dutifully mounted the drive it found on the firewire cable.

None of which would be a problem if I’d gone with the original restore method of booting the Leopard DVD and using Disk Utility to restore the backup.

My bootable backup partition survived, but Time Machine wanted to play with it’s partition that had just come back online; I stopped everything an unmounted as quick as I could (in hindsight unmounting on both machines was my mistake, I should’ve just yanked the cables), but it was too late. It started with Invalid Sibling Links (which was actually quite easy to fix, I’m not afraid of a little fsck) but after the rebuild I’m getting incorrect number of thread records which is unfortunately fatal.

What’s a geek to do? I could just wipe the drive, all it had was my Time Machine data and a few other files that I have copies of on both my second backup drive and my network storage server. But after John Gruber mentioned DiskWarrior the other day, I figured it was a useful investment to make even if it didn’t work. On a side note, I ordered it online because with the Australian dollar over 92c US the 50% markup Australians pay (not just at the Apple store, but that’s the only link I can find atm) is absolutelybeyond fathomable. Even after international shipping I’m saving $30 by ordering from Alsoft directly.

Naturally, DiskWarrior worked and the drive is back. So technically it could be thought of as a $120 mistake, but truth be told DW will probably safe my life again and at the end of the day I’m just glad I made this mistake on non-critical data. Now I know what to watch out for and it’ll never happen again.

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