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Time Machine overwrites older backup data, right?

I am backing up a 1tb iMac and a 2TB media drive (external USB) to a 9TB DROBO FS. For those not familiar with the Drobo, it is basically a NAS with some other features.


My question is: The Drobo is telling me that one of my disks is full. It is my understanding that Time Machine, when encountering a "full" backup destination that it would overwrite the oldest files the the more recent ones. Time Machine is telling me that it hasn't backed up in two weeks because the disk is full.


Thoughts? Either with Time Machine, or if you are familiar with a Drobo.


Thanks.


Oh. iMac, Mavericks.

Posted on Mar 24, 2014 1:15 PM

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Posted on Mar 24, 2014 1:18 PM

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.

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Mar 24, 2014 1:18 PM in response to Kryptae

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.

Mar 24, 2014 4:42 PM in response to Kappy

Thanks,


If I understand this correctly, Time Machine will always be asking for more space once the target disk is full?


Aside from starting with a new backup (which took roughly 5 days the first time) or adding another drive, are there any other suggestions?


I've been using Time Machine prettymuch since it came out and aside from a recent change to a new iMac, I haven't needed to go back to recover anything. I really just have it becuse in case my external media drive dies and I can't transfer the files to a new one.


I'm just looking to keep the most recent backup since I'm adding things regularly.

Mar 24, 2014 6:38 PM in response to Kryptae

Yes. You can use the Time Machine application to remove older backups you feel you no longer need. This will free up space. But once the drive is nearly filled and Time Machine cannot find old enough files to remove then the disk full error will recur.


You can get a larger Time Machine backup drive. But once it gets full you have the same issue. Personally, unless you have a real need to save old versions of files, I find using a backup utility that just overwrites an old version with the new one a better solution. You never run out of space as long as the backup drive is as large as the drive it backs up.


Suggested Backup Software


1. Carbon Copy Cloner

2. Get Backup

3. Deja Vu

4. SuperDuper!

5. Synk Pro

6. Tri-Backup


Others may be found at VersionTracker or MacUpdate.


Visit The XLab FAQs and read the FAQ on backup and restore. Also read How to Back Up and Restore Your Files.

Time Machine overwrites older backup data, right?

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