Restoring after corrupt partition map?

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Level 1

111 points

Restoring after corrupt partition map?

I have what I, and the techies at Micromat, believe to be a corrupt partition map on my 1TB HD under MacOSX.6.8.

I have Time Machine/Time Capsule back-ups.

Our reason for believing this is that I am unable to instal TechTool Pro's edrive as the installation process cannot create a new partition - and neither can I using Disk Utility. The error messge returned is ...

The partition cannot be resized. Try reducing the amount of change in the size of the partition - which latter entreaty makes no difference.

If, after reformatting the HD from the OSX instal disk, I then "Recover the entire hard drive" from the Time Capsule, will that also carry across the old and unwanted corrupt partition map? Or will it lay all the files down under a new and correct map?

Or do I need to "migrate" the Time Capsule data to the newly formatted HD and, if so, at what point should I apply the OSX.6.8 combo updater? Before migration (when there will presumably be no netwrok settings, etc. carried over so without doing that manually there won't be an internet connection) or after migration? Or would the very act of migrating update the OS from 6.0 to 6.8?

I'm not very techie minded and don't want to create any more self-inflicted trouble than necessary!

Thanks in advance.

27" quad-core i7 iMac-OTHER, Mac OS X (10.6.8), 16GB RAM; G4 eMac & Tower; iPad 4G

Posted on Dec 15, 2012 1:17 PM

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Answer 1

Best reply

steve359

Level 6

17,169 points

Dec 15, 2012 1:33 PM in response to iBozz

Not necessarily corrupt.

Over time, as files are deleted and that space reused, even OSX "file fragmentation correction" cannot keep up.

Sometimes the disk space has just been used/reused too much for "resize down" because there are to may 1 and 2 block sections of the disk space unused.

Reformat will clear all, and TIM restore will line all of your ducks back up in a clean row, with much free space left and few unused blocks.

Curious ... what do you think TechTool Pro is going to do that OSX cannot clean up by itself?

EDIT BY steve359

Go to DiskUtility, select the partition, run "Verify" to see if the file structure is still intact, which it may well be.

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Answer 2

iBozz Author

Level 1

111 points

Dec 15, 2012 2:05 PM in response to steve359

Thanks, Steve.

In reverse order ...

I've run Disk Utility Verify and it reports all is well, although I did need to repair the drive a few days ago.

I have also recently run fsck -fy and OnyX and applejack AUTO restart after a series of four kernel panics in as many days. They, at least, appear to have stopped after those "clean-ups" so I am presuming (and hoping) that they were caused by a software/systems glitch, probably caused by a number of power failures here whilst the electricity company enjoyed themselves replacing some defective mains supply cables in the road!

What do I think TT pro will do? Well, five or more years ago I was having serious trouble with an all-in-one original iMac and a techie Mac friend then recommended TT Pro as a diagnostic to try and trace the cause - it turned out to be a failing capacitor resulting in a deceased iMac.

More recently, I acquired the current version of TT Pro as part of a discounted bundle of software offer from MacUpdate(?) and I decided to install the edrive - which I understand to be a logical drive into which one can boot if there is ever any trouble with the main drive. Maybe belt and braces but, I thought, it can do no harm and might come in useful one day. However I failed, even with help from Micromat, and they are the ones who "diagnosed" the corrupt Partition Map as the probable cause. Apparently, and according to them, TT Pro can diagnose many things (and cure AIDS and bring world peace I shouldn't wonder), but not a corrupt partition map!

To be quite frank, I didn't even know that I had a Partition Map so wasn't in any position to doubt them!

OK, I can understand Reformat, which is what I intend to do, but which restore option do you mean by TIM restore - "Recovering the whole hard disk" (David Pogue's The Missing Manual, p 258) or installing OSX6.8 from the instalation disk and then migrating the data from "an old Mac" to "a new Mac"?

Apologies if I sound a bit dim, but as i said I'm not a techie.

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Answer 3

steve359

Level 6

17,169 points

Dec 15, 2012 2:27 PM in response to iBozz

We all need to learn. Just the fools refuse to admit there is anything else they need to learn.

PARTITIONS

All disks have a partition map. Apple OSX uses GUID to allow HFS+ (Extended journaled) partitions. BootCamp modifies it slightly to allow an NTFS partition to load Windows.

Windows uses a MBR (Master Boot Record) partition map for Windows-style partitions.

TOOLS AND CLEANUP OF DISK ISSUES

Kernel crashes can happen, as the underlying storage of files degrades. Supposedly OSX prevents this by regularly checking for bad disk sectors and moving files on those bad areas. But over time all disks die and OSX is not designed to be overly-aggresive sekking out bad sectors, unless it is performing a format.

Your disk may be showing its age. Be prepared for a new disk soon when OSX says it is time (does not mean tomorrow, or next week, or ... but probably within 2 years).

Third party tools often do more harm than good, even of that harm is only to tell you things that do not need to be fixed.

Onyx is not recommended by many senior forum contributors. And TechTools should just be avoided and let OSX do its work.

RESTORE OVER TM. (I misspelled TM -- TimeMachine -- as TIM, sorry)

I prefer a clone for this operation. CarbonCopyClone costs $40 as download. It makes a bootable (recovery device) backup. You then clone again and it moves over only changed files, shifting old ones around the clone to leave you a fully bootable disk (such as for times when your main disk just dies).

TM is not bootable, to my knowledge.

I would download CCC (well worth the $40). Get another external drive (why not a new drive for this operation). Then make the clone. Test the clone by booting into "option" key at startup, to select the clone. Use that clone for a short while (3 minutes, 5 minutes, 10minutes, 4 hours ... your call) until you are sure that clone is a valid copy.

Then you can use the DiskUtility on that clone to reformat your internal partition as "extended journaled" which should hopefully pick up more bad sectors that were just waiting to die. Then clone back and you are right where you left off.

That clone-format-reclone is a good exercise for the time you really have an emergency and are scr%wed without the bootable backup.

Read this for more, then report back:https://discussions.apple.com/docs/DOC-3045

Do not worry ... *someone* in this forum, if not me, knows how to walk you through this. AND you have warnings about disk going bad instead of it just dying and you have no plan to recover.

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