What happens when backup drive is full?

About TM "Backup Drive is Full" Alert

TM only deletes older files if they have been deleted from the source and when TM needs space on the backup drive for a new incremental backup. Time Machine "thins" it's backups; hourly backups over 24 hours old, except the first of the day; those "daily" backups over 30 days old, except the first of the week. The weeklies are kept as long as there's room.

So, how long a backup file remains depends on how long it was on your Mac before being deleted, assuming you do at least one backup per day. If it was there for at least 24 hours, it will be kept for at least a month. If it was there for at least a week, it will be kept as long as there's room.

Note, that on a Time Capsule the sparsebundle grows in size as needed, but doesn't shrink. Thus, from the user's view of the TC it appears that no space has been freed, although there may be space in the sparsebundle.

*Once TM has found it cannot free up enough space for a new backup it reports the disk is full. You can either erase the backup drive and start your backups anew or replace the drive with a larger drive.*

What is the capacity of the drive you backup? Your TM backup drive should be at least twice the capacity of the drive it backs up. Of course you can free up some space by using the TM application to delete older backups (don't try to do this manually. Use the TM application.)

Also, see User Tips for Time Machine for help with TM problems. Also you can select Mac Help from the Finder's Help menu and search for "time machine" to locate articles on how to use TM. See also Mac 101- Time Machine.

From: Mac 101: time Machine


"Backup disk fills up"

As your backup disk begins to fill up to its capacity, Time Machine intelligently deletes the oldest backups to make room for newer ones (and will alert you if the "Warn when old backups are deleted" option is selected in Time Machine preferences).

If your backup disk is filling up often causing your oldest available backups to be erased sooner than you might want, consider the following options:

* Use an additional disk for your backups or transfer your backups to a new, larger disk as detailed above. When you connect a new disk for the first time, use Time Machine preferences to select the disk. Tip: You can also browse the original backup disk for past backups by using "Browse other Time Machine Disks"--to see this choice, hold the Option key then click the Time Machine menu in the Finder (to see the menu, "Show Time Machine status in the menu bar" must be selected in Time Machine preferences.

* Reduce the amount of information being backed up by adding to the "Do not back up" list in Time Machine preferences, as mentioned above. Your backup disk will fill up less often.

* Delete file(s) that are no longer needed (such as from your desktop, Documents folder, or other Home folder locations), so they will no longer be backed up. You can also enter the Time Machine restore interface and find files that can be removed from the backup disk itself to conserve space. To do this, select the file(s) and from the Action pop-up menu (gear icon) in the Time Machine Finder window choose "Delete All Backups of...". Be sure to only delete files you are sure you won't need or want to restore later.

If you read what I posted then you should understand that TM does delete older files to make room for new ones, but if it cannot delete enough old data to accommodate the amount of space needed by the new backup, then you will get the full disk alert.

You can open the Console application and find the information on the backup to see how much space TM is looking for (or use Time Machine Buddy to see the information.) You might them use the TM application to try deleting enough unwanted backups to provide the space.

Alternatively, erase the backup drive and start over; or get another backup drive that is larger.

Ian Chamandy1 wrote:
TM is not intelligently deleting old files. It is telling me my disk is full and it is not backing up. Also, my understanding from the post above is that TM doesn't actually delete my oldest files to add my newest ones. So I am still confused!

If it is supposed to delete my oldest files to add my newest ones, how do I get it to start doing that?

According to your signature, you're running Leopard; but you've posted in the Snow Leopard forum.

This is handled differently on Leopard vs. Snow Leopard. If you're really on Leopard, remove the check from the +Warn when old backups are deleted+ box in +Time Machine Preferences > Options.+

If not, or if that doesn't help, see #C4 in [Time Machine - Troubleshooting|http://web.me.com/pondini/Time_Machine/Troubleshooting.html] (or use the link in *User Tips* at the top of this forum).