Q: Time Machine restore point failure - a WARNING!
I have an iMac 21.5", Late 2012, which has spontaneously died three times, so Apple are going to replace it (and good on them for that too!). Usual question from the Genius Bar techo - 'do you have a backup you can restore from, or should we data migrate for you?'
The iMac (10.8.2) in question has had, since it was installed in December 2012, an external HDD, selected as (and exclusively so) the Time Machine backup drive. It has faithfully done its backups once a day daily (using Time Machine Editor to adjust frequency of backups). I've used it to 'go back in time' to restore various files over the past six months no problem. Looking into the mounted sparesimage you can see and access the dailies. This iMac had gone through 10.8.2 > 10.8.3 > 10.8.4 updates before it died.
So, to be able to answer the Genius Bar techo, I hooked it up to my 10.8.4 iMac, booted into the recovery partition, selected Restore from TM backup option for this drive, and found out that the last actual 'restore point' was actually months ago!!! Even though TM had been dutifully and (proven) done the TM backups, it's official 'restore point' is actually way months - so all the data accumulated/changed since then is actually not restorable through Migration Assistant, and would have to manually restored piecemeal from the retsore point!!
Bottom line: in this particular case, the HDD is OK - so a clone from the old drive to the new iMac's drive is OK. However, had the old iMac's drive failed in any way, the daily Time Machine backup would have been worthless as a 'restore-and-go' backup.
So - be warned: check the state of your Time Machine backup by looking to see what it's last 'restore point' actually is. If it isn't your last backup, as far as i can tell, deleting the current TM backup, and starting over again is the only way forward for a 'restore point' backup; if you need the incrementals, then get a new backup drive and harness that.
[Notes: I'm talking from a purely Mountain Lion perspective - I can't say for other iterations Leopard-onwards.
Also, for the record, my other iMac's external third-party backup drive recently failed and was replaced, and the (now) 10.8.3 > 10.8.4 TM backup restore point is today current from that point forward - so I can't give another historical perspective on whether it was a particular update that might have caused the restore point issue].
Posted on Jun 11, 2013 12:32 AM