Time Machine backup size

[Durbs]

I've not backed my mac up before, just used Dropbox for any important stuff but now have a 2nd Mac so would like to back them up 'properly'.

Have bought a little Iomega StorCenter iX2 2TB NAS box (which i'm chuffed with and would recommend to anyone after some network storage) and have set up Time Machine on both Macs.

Reading up on this Time Machine thing it seems it'll just churn away taking hourly, weekly and monthly backups until it runs out of disk space! Can't see any way to define a cap on it and given i've got a few hundred Gig of other data that i bought the NAS for i don't want Time Machine taking up any real space on the disk.

Creating a separate partition on the NAS isn't an option (don't know whether I can and wouldn't want to anyway), does anyone use Time Machine and limit its space somehow?

[xisystems]

For information my Macbook pro Time machine image is 120ish GB for a 500GB with 100ish GB used. I recently had thoughts of why bother with time machine as all my company information was backed up on a server and it seemed to be adding no value, however Time machine proved brilliant at the weekend as the Hard drive failed in my Macbook pro and I was left with a lump of useless aluminium. A Trip to mac store ended up with a new Macbook pro with the feeling of oh boy hours of application re-installation and data recovery. However when I returned home all i needed to do was select the restore from time machine option and the new machine was all set up as the previous one (applications, preferences, documents you name it) saved me hours of rebuilding it! for this Time machine instantly made it self something I will be running without a second thought!

hopefully my experience proves useful to someone!

Simon

[bogeyman]

I'm pretty sure that TM will just fill up the space available. I don't think there is a way of telling it to use only so much of the available backup volume. There are a few threads on discussions.info.apple.com about this, but no real answers.

Personally I think TM is a bit of a crock, and after some initial experimenting (and diminishing enthusiasm) I decided to turn it off on my Macs.

For my main desktop Mac I use SuperDuper to back up to a local Firewire 800 drive (LaCie Quadra 2TB) so that I have a bootable image copy, should the main machine go tits up. This has actually happened (iMac PSU problem) and I was able to boot my MacBook Pro from the SuperDuper backup FW drive and, despite the obvious hardware/screen size differences, it worked pretty much perfectly. Try doing that with a Windows desktop laptop combo (or a Linux setup for that matter).

Of course SuperDuper only gives you the latest image copy, and TM gives you versioning. The only data on my Mac that matters to me with regard to versioning is code-related. Everything else is either static or easily recreatable. I use other versioning solutions for code etc. which back up to external servers, so I don't feel Time Machine offers me very much.

Personally I feel safer with a bootable image backup that can recreate my primary machine in its last good state. AFAIK Time Machine still does not provide a bootable image backup.

[NickFitz]

You can configure Time Machine to use a sparse disk image on NAS, but you'll have to do a bit of stuff at a command line in Terminal. EDIT: also, be sure to check the comments to that hint, and do some judicious Googling around the key terms to see if any new information has come to light about the best options for such configurations. N.B.: I haven't actually tried any of that stuff, so don't blame me if it goes wrong

As bogeyman says, SuperDuper is wonderful for keeping a bootable image. Time Machine is good for versioning of day-to-day data, and some other version control system is essential for code. I use SuperDuper as my main backup strategy for the MacBook which is my primary machine, and Subversion for version control (which isn't actually the same as backing up in a purely philosophical sense, but wotever).

I would use Time Machine but it would be inconvenient to keep an external USB drive hooked up to my MacBook all the time, as I work in my armchair and the drive would occupy the space I need for my coffee mug. (It can't go on the other arm because of the pile of books.)

[Durbs]

Thanks chaps.

Seems strange they didn't add a 'limit backup size to......' option. Will take a look at that SuperDuper thing. When buying the drive I thought "2TB, thats virtually infinite space!!!!!" but once i'd set up mirroring (now 1TB, still huuuuge though) and added on all my movies, music, code, backups for 2 macs, 2 PC's and a server then it wasn't big any more

Nearly went for the 4TB one but thought there was no way i'd need that sort of space. Doh. You dont realise how much crap you've got data-wise until you bung it all into one place.

Had a look at that workaround Nick but all seems a bit voodoo for the sake of a backup! Got an SVN instance running for my code so may just look at doing an occasional manual backup in SuperDuper or summat.

[Sysman]

A few observations on Time Machine:

• Yes, it will fill up the target disk. This is not catastrophic; it will ask for another disk, but you can tell it to go ahead anyway, whereupon it will delete the oldest backups.
• In order to get a summary of how much is backed up and when, and see which backups are retained in the hourly/daily/weekly cycle grab a copy of Back In Time. It's 29 Euros or 29 USD, but you can run it in demo mode for as long as you like. Demo mode only allows you to perform operations on the most recent backup, but you still get to see the summary listings for all backups.
• Time Machine will only perform backups when an interactive user is logged in. For example, if you set your system to wake at 6 am, until you actually climb out of bed and log in, Time Machine will do nothing.
• Backups are by default performed at 60 minute intervals after the system was started. This is independent of the time you logged in, although if you log in "just after" the hourly 60 minute interval, Time Machine will kick in. This can be a pain when all you want to do is login to check your mail, and the system is busy doing backups. I tend to leave mine logged in, with a password protected screen saver.
• If you have your laptop set up for Time Machine, you don't need to switch Time Machine off when you disconnect it from external disks to take it on your travels. TM will simply start processing again when it sees the TM disk connected again. TM will start issuing warning messages if it hasn't run for 10 days. I take the precaution of powering my laptop down before disconnecting to ensure external disks are dismounted correctly.

Remember also that while fine for client backups, Time Machine is not really designed for server backups. Think open files and databases here. I do regular PostgreSQL and MySQL dumps separately.

[Durbs]

Ta.

Time Machine will only perform backups when an interactive user is logged in. For example, if you set your system to wake at 6 am, until you actually climb out of bed and log in, Time Machine will do nothing.

Didn't know that. My Mac Mini was part way through its first TM backup last night when i switched it off. I pressed the power button on my way out of the house this morning hoping it'd churn away today but as i didn't log in i guess not

[Sysman]

Ta.

Didn't know that. My Mac Mini was part way through its first TM backup last night when i switched it off. I pressed the power button on my way out of the house this morning hoping it'd churn away today but as i didn't log in i guess not

I'm not sure this applies to OS X Server, but is certainly true for the vanilla client version.

Edit:

I forgot to add. The daily backup that Time Machine keeps is the first one of the day. Sort of - if it does a backup at say 23:50 which doesn't complete until after midnight, that will be the one that is kept.

[DS23]

I would use Time Machine but it would be inconvenient to keep an external USB drive hooked up to my MacBook all the time...

er... no usb is required (at least not after initial setup)

personally i find time machine excellent* - it has saved my bacon a few times. it filled up some months ago and is currently dropping the oldest files to make space for the newest. it is an ideal way of ensuring a backup strategy is enforced. which reminds me - i must perform my alternative backups for when the tm and macbook fail at the same time.

* i do recall a year of cursing, resetting the unit and cursing again until a suitable software update was released to make it work as advertised. until then it was only useful as an apple tv lookalike as in: "oooh - have you got apple tv?" "no, it's a time machine that doesn't work".

[Ignis Fatuus]

er... no usb is required (at least not after initial setup)

personally i find time machine excellent* - it has saved my bacon a few times. it filled up some months ago and is currently dropping the oldest files to make space for the newest. it is an ideal way of ensuring a backup strategy is enforced. which reminds me - i must perform my alternative backups for when the tm and macbook fail at the same time.

Absolutely. If you need a backup, then you need at least 2, because you probably won't find out that 1 has failed until you need it.

You can do Time Machine to >1 backup disk, by choosing which disk to backup to, in Time Machine Preferences.

I have heard that TM can corrupt several backups if it has a problem (like network drop or cable prob), and in some cases will blithely tell you that the entire backup disk is unreadable, and that the action to take in order to continue is to format the disk and resume making backups.