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A possible disk-format-related cause of general Mac issues System
As the informal Mac support guy at work (a role many of us Mac users are no doubt familiar with), I had a coworker come to me complaining of a bunch of odd little behaviors on his Mac. Email acted oddly, applications would behave strangely, and sometimes when he first started his Mac, it would display the Net Boot logo for a couple of minutes, time out, then boot normally. When we tried to set his startup disk, we found that it wasn't listed as a choice in the System Preferences panel. Disk First Aid showed no errors, and repairing permissions showed some permission errors, with OS X claiming to have corrected them, but the errors remained on subsequent checks.

After a bit of sleuthing about, I discovered that he had recently swapped out the hard drive, and used Carbon Copy Cloner to move to the new drive. The drive was formatted as HFS+ Journaled, but the partition was MBR (Master Boot Record) and not GUID. Once we re-partitioned the drive, and restored his data, all his problems went away.

The moral of the story: OS X can boot off an MBR volume, but suffers indigestion. Just a little FYI for folks to put into their troubleshooting toolkit.
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A possible disk-format-related cause of general Mac issues | 14 comments | Create New Account
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A possible disk-format-related cause of general Mac issues
Authored by: mchmarny on Aug 10, '09 08:18:17AM

Dude, you have no idea how this has been driving me nuts. I have used super-duper to restore the entire drive the other day and too had been unable to find the reason as to why my drive would not be showing in the start-up volume list.

Well, there goes another 3 hrs of my life: 1.5hr to snapshot the drive (200GB in MacBook), reformat, and 1.5hr to restore it.

Thanks

---
Mark



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Ticking Time-Bomb of Destruction
Authored by: emanhaud on Aug 12, '09 08:32:25AM

I work for a hard drive manufacturer and have to disagree with diamonsw, gabester, and Reaper Man. We have had tons of documented problems with HFS+ volumes on MBR disks both in the lab and in the field. In my experience larger drives will often fail to format in this scenario. Smaller disks will often format properly, but deteriorate over time.

We have changed all of our end-user documentation to tell the user to repartition drives with either GPT or APM instead of reformatting them on an MBR partition map. HFS+ on MBR is a ticking time-bomb of destruction and unhappiness.



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A possible disk-format-related cause of general Mac issues
Authored by: diamondsw on Aug 10, '09 08:31:35AM

I have to think something else was at play as well. I run one system with an MBR formatted OS X disk as well, and have no problems. A case-sensitive filesystem is MUCH more likely to cause the types of issues reported. In general, no OS cares what type of partition map you have, as long as it can find the start and end points of the partition itself.



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MBR and multiboot
Authored by: gabester on Aug 10, '09 09:13:25AM

I used an OS X install or 2 imaged to an MBR partition(s) to multiboot my Mac in the past. Aside from the headache of managing multiple partitions and an issue with the machine locking up completely when disconnecting from a web-based VPN I saw no significant issues that I could relate back to having an MBR partition. I'd even deleted the EFI partition so I could boot into up to 4 windows OS configurations.

I suspect as has the previous poster that case-sensitivity may have been the real culprit. Or something else unusual with the setup.
g=



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MBR and multiboot
Authored by: frgough on Aug 10, '09 12:02:00PM

The only thing that was different before and after was MBR vs. GPT. The machine was behaving fine before the swap, and giving issues after the swap.

The only change we made was changing the drive partition type. There was no other change to the setup Since the data was cloned to a backup then cloned back onto the Macbook.



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A possible disk-format-related cause of general Mac issues
Authored by: Reaper Man on Aug 10, '09 09:39:25AM

> he drive was formatted as HFS+ Journaled, but the partition was MBR and not GUID.

I'd like to correct this terminology. The drive was partitioned as MBR not GPT (ie GUID Partition Table). The partition was formatted as HFS+ Journaled.

I'd have to agree with the other commenters as well. There was something else wrong. This should work fine.

To one other commenter that removed the EFI partition.

While there is regularly nothing on this partition, Apple uses the EFI partition to do firmware upgrades. Removing the EFI partition will likely cause the inability to complete firmware upgrades.




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good way to snapshot?
Authored by: axled on Aug 10, '09 05:57:26PM

I suspect this is what's wrong with my macbook, but I don't have an external drive big enough to back-up my HD to. Is there a way to do this without reformatting, or should i just break down and buy a Time Capsule? and wht's the best way to do it if I do have to buy an external?
Thanks!



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good way to snapshot?
Authored by: las_vegas on Aug 10, '09 07:27:43PM

With a bit of work and the proper utilities (IE: Drive Genius 2), you may be able to create the EFI partition prior to the HFS+ partition.

It would be much easier to use a backup drive (You can pick up a 1T drive nowadays for less that $100) to backup your drive, repartition the boot drive properly and restore.



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how can i tell?
Authored by: fursonice on Aug 12, '09 01:35:50AM

sorry, but how i can tell whether my drive is MBR or GUID?



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mine say APM (Apple Partition Map)
Authored by: fursonice on Aug 12, '09 01:40:45AM

??? which is that, GUID or MBR?



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how can i tell?
Authored by: frgough on Aug 12, '09 06:26:36AM

In Leopard:

1. Launch Disk Utility.
2. Select the drive.
3. Look at what it says under Partition Map Scheme.

I don't know how it looks in Tiger.



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mine says 'Apple Partition Map' ?
Authored by: fursonice on Aug 12, '09 08:12:35AM

which is that?



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mine says 'Apple Partition Map' ?
Authored by: frgough on Aug 12, '09 10:12:34AM

That's for PPC macs. GPT is for Intel Macs.



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mine says 'Apple Partition Map' ?
Authored by: fursonice on Aug 12, '09 09:17:28PM

thanks sawtooth/10.5.8.

i have some disk problems... disk is there folders are there... bootable... but booting from *second* internal (same system) some of the folders files won't show... Finder spins.

(used CCC to clone previously which led me into this tip.)

thanks.



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