HT201250: Use Time Machine to back up or restore your Mac
Learn about Use Time Machine to back up or restore your Mac
-
All replies
-
Helpful answers
-
Oct 27, 2014 3:23 PM in response to ☮by Kappy,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.
-
Oct 27, 2014 3:30 PM in response to Kappyby ☮,There was plenty of space on the backup drive, and the backups were there for at least a week.
What is the definition of "the first of the week"?
-
Oct 27, 2014 5:12 PM in response to Kappyby ☮,Looking at the logs, and assuming that "the first of the week" means when no other saved backups exist in the preceding 7 days, then it looks like what happened was that backupd first decided that 2014-09-19 was expired because 2014-09-13 existed, then the next time it ran, it decided that 2014-09-13 was expired because 2014-09-09 existed.
But (since it had also previously deleted several others by similar reasoning) that left it with no saved backups for several weeks following 2014-09-09,
whereas if backupd had first deleted 2014-09-13, it could have then kept 2014-09-19 since no other saved backups would have existed in the preceding 7 days.
So, assuming the hypothesis that "except the first of the week" means except then no other backup exists in the preceding 7 days, my followup question is how does backupd decide which expired backup to delete first when more than one expired backup exists?
In this case, it's decision seems to have had some unintended consequences.