Time machine out of space / Merging time machine backup I have a 15 inch Mac Book Pro that is my main machine. At some point, in the
second half of 2011 I purchased a 750GB external hard drive to configure Time
Machine on my laptop. This is my main method for backup, and I always keep
it up to date. A few weeks ago it started complaining that it did not have
enough space and that it needed to delete the oldest backup to create this new
one. I allowed this to happen at first, but realized that I was losing possible
important historical snapshots of my data.

I want to purchase a new, larger external hard drive to keep my time machine
backups. Before spending a couple hundred dollars in this project I  have a
couple of questions regarding best practices:


Will TM allow me to integrate my older backups into the new hard drive?
While it seems convenient to have my whole history in one hard drive, would it
be smart to do so? Or should I not integrate them? I understand that this would
constitute a single point of failure that is highly undesirable.
What other advanced practices do people have with TM to not have a single point
of failure?
TM will not move your old snapshots to a new drive, although I'm pretty sure that if you first used Disk Utility's Restore tab to clone your old backup drive to the new one (after reformatting it properly), it would see the old snapshots properly.

But there's a bigger problem. You are trying to use TM as an archiving tool, but that's really not what it's designed for. TM will expire old snapshots as it sees fit, so if you want reliable retention of old files it's not the right tool for the job. Unfortunately, I don't have a good suggestion for a better tool, but I would strongly recommend looking for something more appropriate.

That said, switching TM to a new drive (and removing the old one from its backup target list) would be a semi-reasonable way to retain all of the old snapshots (and having multiple redundant backups is a good idea). Doing that and switching to a new archiving tool would also be reasonable (since you probably won't be able to migrate the old TM snapshots to any net tool you select).