Time Capsule - How large are the backup files?

[brachson]

Hello,

I have base 21,5'' 2011 iMac with used 250GB/500GB

I am planning to buy TC but cannot find the information how many backups I will be able to do. 250x4 = 1TB so if I will decide to backup all my files I will be able to make 4 copies from let’s say last 4 days??

How does it work?

 

[Ivan P]

The way it works is that the first backup will copy EVERYTHING on your computer to the backup drive - so if you are using 200GB of your hard drive then the backup will be 200GB. Every subsequent backup only backs up whatever has changed on your computer. So, for example, if you copy 1GB of music to your computer and then perform another backup then only an extra 1GB of data will be copied to the backup drive.

Time Machine, the program that will backup your computer to Time Capsule, performs backups every hour, then consolidates them into a daily backup that represents the last week's worth of changes; after a week these daily backups are further consolidated into a weekly backup. Every time one of these backups occurs, it doesn't copy your entire hard drive again, it only copies the changes. If the backup drive becomes full then it will simply delete the oldest backups automatically.

 

[brachson]

smart! So if I have 500gb on my iMac TC with 500GB would be also enough as I can not have more that 500GB to be backuped ever - correct?

 

[Macman45]

Yes

smart! So if I have 500gb on my iMac TC with 500GB would be also enough as I can not have more that 500GB to be backuped ever - correct?

And even if the drive reaches capacity, TM dumps the oldest backup first, and carries on that way.

I have a 500gb external I use for backup, and it's got lots of space left, nowhere near the limit.

 

[gr8tfly]

smart! So if I have 500gb on my iMac TC with 500GB would be also enough as I can not have more that 500GB to be backuped ever - correct?

Besides the fact that you wouldn't want to run your system on a full drive, that wouldn't leave any room for future backups. The whole idea of Time Machine is to both completely backup your HD and to allow you to retrieve previous versions or retrieve accidentally deleted files. Cases where there are a large number of files changed - for instance when a system update happens or after application updates, there could be easily many GB worth required for backup. Each time this happens, it increases the total space taken up by the Time Machine backup.

Since Time Machine automatically deletes the oldest backups when the partition is full, this limits how far back in time your backup goes. A good rule of thumb has been to have a Time Machine partition ~2x the space you normally use. So, if you typically use say 400GB out of your 500GB drive, then a drive between 750MB and 1TB would be appropriate. Given the price of drives these days, you might as well go with the 1TB.

 

[driftless]

FWIW - Apple dropped the 1TB TC and now offers a 2 & 3 TB version.