PDA

View Full Version : Relative integrity of TM vs original drives




robgendreau
Aug 29, 2013, 01:41 PM
I have a dying drive (not sure specifically what ails it; it's throwing SMART error and beachballing, but I have been able to continue to backup/copy stuff and run things without ill effect, and directories seem OK).

I'm gonna install a new drive and then use Setup Assistant to migrate things over. In the past I usually did that with the drive I had just removed as the source rather than using my TM backup because I'm usually moving it to an enclosure and it's right there. Always worked fine.

But given the drive is dying, and since I don't wanna get hours into it and have to start over, I'm gonna use the TM drive this time.

I'm wondering if the TM drive is likely to have more integrity than the current, dying drive, or if it's copying over problems to the backup. Does TM automatically check files to see if they're at least complete (I obviously can't avoid having some files that have internal problems; until they're used you can't necessarily tell if they're borked)?

Secondly, when you use Setup Ass't (the thing that runs when you first boot after installing ML, as opposed to Migration Ass't, although they do almost the same thing) can you have the option of selecting a SPECIFIC TM backup to use for Migration purposes?

I don't want to do a restore, BTW. Faster, and I don't need what it does.



Bruno09
Aug 29, 2013, 01:59 PM
Secondly, when you use Setup Ass't (the thing that runs when you first boot after installing ML, as opposed to Migration Ass't, although they do almost the same thing) can you have the option of selecting a SPECIFIC TM backup to use for Migration purposes?


No, you can not select a specific TM backup when using Setup Ass't : only the last backup is usable.

However, you CAN choose a specific backup if you boot from the Recovery HD and choose "restore from a TM backup."

In your case, I would use a clone : clone your dying drive to an external drive, check if this clone runs fine, if yes, install this new drive in the Mac.
It is that easy, IMHO (assuming your dying drive is not dead yet).

(NB : or clone your dying drive to an external drive, check it, if ok then clone the external drive to the new internal drive.
Carbon Copy Cloner copies the Recovery HD, which is fine).

robgendreau
Aug 29, 2013, 03:51 PM
I don't see the relative merit of a clone over a restore, and it's even slower (not to mention the time needed to make a new clone). And I wouldn't want to clone a failing drive in any case, lest I simply clone errors. That's why I was asking about any built-in error correction in TM backups or the migration process, although I guess I wasn't clear enough. Thanks though.

I abandoned the use of clones quite a while ago, and haven't missed them for my uses. Migration usually works great and is SO much faster.

Bruno09
Aug 29, 2013, 04:01 PM
I don't know if your drive is dying "physically" or "logically" (or both).

If you made a clone, you could boot from it, and see what happens when using it :

- not better than your HD ---> ok, think TM.

- everything is ok ? ---> clone the clone to the new HD

Also please note that CCC does checks for corrupt files.
See : http://help.bombich.com/discussions/questions/42644-if-original-file-becomes-corrupted

robgendreau
Aug 29, 2013, 04:17 PM
I don't know if your drive is dying "physically" or "logically" (or both).

If you made a clone, you could boot from it, and see what happens when using it :

- not better than your HD ---> ok, think TM.

- everything is ok ? ---> clone the clone to the new HD

Also please note that CCC does checks for corrupt files.
See : http://help.bombich.com/discussions/questions/42644-if-original-file-becomes-corrupted

I understand, but I can't afford that much down time. If it works well it only gets me to the same place that a migration does, but at the expensive of a whole lot more time. And I'm betting it's 50/50 the drive wouldn't last that long.