OSX Lion Time Machine

Nov 9, 2011 3:54AM PST

All of a sudden, Time Machine lost its association to my external drive's backups.
I know I can start a fresh backup. The choice is there, but I would like to continue using the same backups since I've been doing them for over a year.What gives?

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Could be a corrupt Sparsebundle.
Nov 9, 2011 5:27AM PST

if the drive is still available for use as a TM backup destination, just use it.

Although the backups will probably start over, remember that TM is not designed as an Archive device.


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Nov 11, 2011 8:10AM PST
"TM is not designed as an Archive device."

Can you expand on this?

What does it mean?

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The differences between
Nov 12, 2011 5:04AM PST

Archive and Backup.

High media capacity
High-performance read/write streaming
Low storage cost per GB

Performance is an important factor for backup, but since most backup operations involve large data sets, the ability to quickly stream information to and from the backup media is a first priority. Fast random access to small data sets during restore operations is typically less important. As an insurance policy, it is also necessary to minimize backup expense by reducing the cost of each stored record. The media of choice for backup and disaster recovery applications has traditionally been magnetic tape since it satisfies the performance and cost criteria of most organizations.


Data authenticity
Extended media longevity
High-performance random read access
Low total cost of ownership

Archival storage requirements are quite different from those of backup operations. Media longevity and data authenticity feature much more prominently in archive environments. The storage media used within an archive should have a stable, long life to avoid frequent data migration over decades of storage. In order to comply with corporate and government regulations on data authenticity, it is crucial that information be protected from modification.

Bottom line:
Time Machine is a backup system that will, once the capacity of the drive has been reached, delete old files in order to continue to backup.
This deletion process means that Time Machine cannot be classed as an Archival system.
Remember too that Time Machine is running on a Hard Drive which, as we all know, is going to fail at some point. Once it fails, the data are gone.


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Archive media and file format
Nov 12, 2011 11:06PM PST

Great explanation!

I can now see your disticntion. Would it be safe to say Backup is recent past and Archive is total past? By this definition would you say Time Machine is an archive for a limited span of time, as far as the point at which the oldest file is deleted?

This brings up other questions for me, maybe a little off topic but related.

What is the media for today's "Archive?"

Is it still tape? Writable CDs & DVD on have a reported life span of only 10 years at best. What will still be a viable medium in 10 years? Is it just cheaper HD storage? Will Flash RAM memory get cheap enough or have enough durability to be the medium of choice?

The same goes for file formats. My family is looking to create a genealogical digital "archive" of photos, video and documents. What file format will still be standing in 20-30 years? PDF? JPG? MPEG? So not only is there a decision to be made on what media to use to put files on, what format should the files be to have the best chance of surviving!

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Interesting subject.
Nov 13, 2011 4:44AM PST

and one that is worthy of discussion, especially the part about which formats will still be around in 30 years.

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Nov 13, 2011 10:41AM PST

I start with a question about my backup problems and now the topic is about freakin NASA and irrelevant archive formats.
Maybe I should have posted a question about a flux capacitor, then I would have had someone help me with my Time Machine backup.
I wonder if anyone read the initial question or they just like to listen to themselves geek out.

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Nov 13, 2011 12:19PM PST

You are absolutely correct...we got off on a tangent.

Your task is to reconnect the existing TM backups you have so TM continues as if it had never got disconnected. While I do not have the actual experience with the difficulty you are having, this article at least touches on the terminal task to reconnect. It is talking about a similar situation, not exactly what you are expereinceing.

Here is another suggestion, involving the plist of TM - sounds a little simpler to at least try first.

And here is an article that was suggested might be your problem in the first post but the geek stuff here is way over my head.

Again, sorry about the tangent.

What was your question about your flux capacitor? :- p

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