Missing Disk Partition after Yosemite Install (invalid sector size)

Question

Missing Disk Partition after Yosemite Install (invalid sector size)

Right off the install, my exFAT partition on my MBP is missing. Thought it was not mounted automatically so I went to Disk Utility to have a look.

It says "invalid sector size (0)" or something (I'll edit/update this post in a bit. I'm on Mac Recovery as I'm typing this) and it couldn't repair it.

Bootcamped into Windows and the same thing's happening (partition shows up but as an unformatted volume, proceeds to prompt to format partition)

I haven't thought to check to see if the OSX volume has expanded or not, so I'll do it after this.

Man I hope the files are still there. Is there a fix or way to manually edit the sector size?

Would reverting back to Mavericks be able to repair it?

Disk Details:

960GB Crucial M500 SSD

Partitioning Order:

NTFS (W7) 128GB | exFAT (stuff) 512GB | HFS (OSX) 256GB | freespace (not used) the rest

(Windows reports a more complicated partition map due to the Hybrid MBR partition map, but the main partition order is as above)

(As for why this order, it happens that I am unable to add an additional partition when I install OSX before Windows due to constraints of the MBR-type partitioning, but I am able to add one when Windows is installed before OSX as a workaround to save one partition count in the MBR)

Mac Details:

MBP 15" Mid-2012 Model A1286 4GB RAM

OSX 10.10 (Yosemite)

Windows 7 via Bootcamp

MacBook Pro, OS X Yosemite (10.10)

Posted on Oct 17, 2014 4:19 AM

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Answer 1

Best reply

putnik

Level 4

1,179 points

Oct 17, 2014 4:25 AM in response to DirectionsNeeded

I don't know if this is your problem and think, from past experience, that any Bootcamp partition needs to be made using the Bootcamp app and after installing a new OS. However, please note that the Yosemite installer may change your disk to Core Storage and try to get you to use File Vault (You can uncheck the option during the install process). But, Core Storage only allows two partitions, so if you have more, you may need to sort that before trying to install Yosemite.

It may help to boot into the Recovery Partition and run Repair Disc from the Disk Utility

http://support.apple.com/kb/HT4718?viewlocale=en_US&locale=en_US

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Answer 2

Oct 17, 2014 5:22 AM in response to putnik

Hi putnik, thanks for the reply. I've tried the repair in Disk Utility from the recovery partition and it's unable to fix it as well.

The installer didn't have any prompts regarding File Vault (I never turned it on in the first place) beforehand.

It's my first time reading of Core Storage, so that may have bitten me on this end. The interesting property of the exFAT volume is Disk Utility recognises that as a Bootcamp volume (although no OS was installed in it and it doesn't appear in Bootcamp). (EDIT: it said that when I still had Mavericks but now it doesn't say anything even with the windows partition)

I'm still looking around for a fix or any way of reading it, and I'm holding off the last resort of reformatting it. Got a few days of work in it that I haven't backed up, although finding a fix could use the same amount of time as redoing it.

Here's the message by the way:

-----

Verifying volume “disk0s3”Verifying file system.** /dev/rdisk0s3

Invalid sector size: 0

File system check exit code is 8.

Error: This disk needs to be repaired. Click Repair Disk.

Verify and Repair volume “disk0s3”Repairing file system.** /dev/rdisk0s3

Invalid sector size: 0

File system check exit code is 8.

Updating boot support partitions for the volume as required.

Error: Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files.

-----

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Answer 3

Oct 17, 2014 6:14 AM in response to DirectionsNeeded

Okay I got everything back. Ran chkdsk on Windows and it recovered the sector listing. Think it's because the exFAT partition is managed under the MBR instead of the partition manager for the HFS Partition. Doesn't explain why would the installer mess with the partition maps though.

Sorry for any undue stress to anyone on the fence on installing Yosemite.

Summary of process:

- Verify both ends exhibit behaviours caused by the same problem (i.e. volume has no specified sector size, causing it to show that it's invalid, blank, unformatted or empty)

- Run Disk Utility and attempt to fix disk. First in OSX, then in OSX Recovery if it doesn't work.

- If unable to fix: Boot to Windows, run Command Prompt as Administrator, and run:

chkdsk (volume label of affected disk) /f

for example:

chkdsk D: /f

!-- Please seek help and advice before attempting to carry out fixes described this thread.

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