Caution - Yosemite may screw up partitions.

[KoolAid-Drink]

I also noticed this on my iMac today. Yosemite partition is now the core volume...

My late-2012 iMac is on 10.8.5. Could the change in core volume harm the main start-up volume in any way? (corrupting files, changing core settings, making certain things now work, etc.)

Also, does this affect how Time Machine backs up the core volume?

Thanks.

Interesting. Bolding below is mine. Looks like the parameters aren't always consistent, if iMacs are also being converted (as iMacs aren't considered portable; not yet, anyway...).

Some members in this thread have pieced together the answer to your second question. It seems to be:

1. Machine is a portable
2. CPU supports AES
3. No Bootcamp partition present

Then you get converted to core storage at Yosemite install.

Now as to why, I think everything to this point is just speculation since Apple has not said why.

 

[e93to]

Interesting. Bolding below is mine. Looks like the parameters aren't always consistent, if iMacs are also being converted (as iMacs aren't considered portable; not yet, anyway...).

Only MacBooks were supposed to be affected? What's wrong with my iMac?!

Other than that, I have a feeling that the partition has slowed down my start-up volume (10.8.5)... Animations are laggy and choppy. And opening files are not as smooth as before.

 

[Weaselboy]

I also noticed this on my iMac today. Yosemite partition is now the core volume...

My late-2012 iMac is on 10.8.5. Could the change in core volume harm the main start-up volume in any way? (corrupting files, changing core settings, making certain things now work, etc.)

Also, does this affect how Time Machine backs up the core volume?

Thanks.

No, other than limiting your ability to resize and manipulate partitions, it makes no difference in day to day operations. Time Machine and everything will work the same.

 

[e93to]

No, other than limiting your ability to resize and manipulate partitions, it makes no difference in day to day operations. Time Machine and everything will work the same.

Thank you!

 

[grahamperrin]

The Apple_Boot slice/partition

Not specific to Yosemite

Can someone tell me what the Apple_Boot partition is? I've tried creating some Core Storage units, and every time i do so, it creates an Apple_Boot partition that's named "Boot OS X" …

Here, with Mavericks:

sh-3.2$ sw_vers ; diskutil list /dev/disk0 ; diskutil list /dev/disk5
ProductName:	Mac OS X
ProductVersion:	10.9.5
BuildVersion:	13F34
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *750.2 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage                         616.0 GB   disk0s2
   3:                 Apple_Boot Boot OS X               134.2 MB   disk0s3
   4:          Apple_CoreStorage                         133.2 GB   disk0s4
   5:                 Apple_Boot Recovery HD             650.0 MB   disk0s5
/dev/disk5
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk5
   1:                        EFI EFI                     209.7 MB   disk5s1
   2:       Microsoft Basic Data PC-BSD                  250.0 GB   disk5s2
   3:                  Apple_HFS 10.9.5                  199.9 GB   disk5s3
   4:                 Apple_Boot Recovery HD             650.0 MB   disk5s4
   5:                  Apple_HFS Graham                  684.1 GB   disk5s5
   6:          Apple_CoreStorage                         665.8 GB   disk5s6
   7:                 Apple_Boot Recovery HD             650.0 MB   disk5s7
sh-3.2$

And:

sh-3.2$ diskutil mount readOnly /dev/disk0s3
Volume Boot OS X on /dev/disk0s3 mounted
sh-3.2$ diskutil info /dev/disk0s3
   Device Identifier:        disk0s3
   Device Node:              /dev/disk0s3
   Part of Whole:            disk0
   Device / Media Name:      Booter

   Volume Name:              Boot OS X
   Escaped with Unicode:     Boot%FF%FE%20%00OS%FF%FE%20%00X

   Mounted:                  Yes
   Mount Point:              /Volumes/Boot OS X
   Escaped with Unicode:     /Volumes/Boot%FF%FE%20%00OS%FF%FE%20%00X

   File System Personality:  HFS+
   Type (Bundle):            hfs
   Name (User Visible):      Mac OS Extended
   Owners:                   Enabled

   Partition Type:           Apple_Boot
   OS Can Be Installed:      No
   Media Type:               Generic
   Protocol:                 SATA
   SMART Status:             Verified
   Volume UUID:              67280920-1D8C-3471-BBB3-D5A3FDD44813

   Total Size:               134.2 MB (134217728 Bytes) (exactly 262144 512-Byte-Units)
   Volume Free Space:        122.6 MB (122646528 Bytes) (exactly 239544 512-Byte-Units)
   Device Block Size:        512 Bytes

   Read-Only Media:          No
   Read-Only Volume:         Yes
   Ejectable:                No

   Whole:                    No
   Internal:                 Yes
   Solid State:              No

sh-3.2$ ls -ahl /Volumes/Boot\ OS\ X/
total 0
drwxr-xr-x  7 root  wheel   306B 28 Jan 00:08 .
drwxrwxrwt@ 8 root  admin   272B  4 Feb 19:09 ..
drwx------  5 root  wheel   170B 28 Jan 00:08 .Spotlight-V100
d-wx-wx-wt  2 root  wheel    68B 28 Jan 00:08 .Trashes
drwx------  5 root  wheel   170B 28 Jan 00:08 .fseventsd
sh-3.2$

In my case, that particular 134.2 MB Apple_Boot slice is effectively empty.

In other situations, an Apple_Boot slice of that size may include boot-related files.

If FileVault 2 is used, then the system must boot from something other than the encrypted OS X startup volume. That thing need not include a Recovery OS.

Hints may be found in open source:

http://www.opensource.apple.com/source/IOKitUser/IOKitUser-907.100.13/kext.subproj/bootfiles.h

http://www.opensource.apple.com/source/kext_tools/kext_tools-326.95.1/bootroot.h

Also:

The Early Boot Process

Technical Note TN2166: Secrets of the GPT – GPT Partition Types

Postscript

In Ask Different, For a FileVault user of Mountain Lion: can I avoid the automated login, which normally follows unlock of the encrypted startup volume? – the accepted answer, Encrypt the startup volume with Core Storage without FileVault. There's a link to an Apple Technical White Paper: Best Practices for Deploying FileVault 2

Recommended reading: within that white paper, Appendix B: FileVault 2 Process Flow

 

[BradHatter]

Not specific to Yosemite...

Thanks. The reference in the Kernel Programming book cleared it up pretty well, so there's one mystery out of the way. I guess with respect to the "why" of Core Storage, only Apple knows. I also find maybe a little wreckless of them to not clearly inform users of the conversion and what it means to their ability to format and partitions drives and volumes.

 

[e93to]

Instructions from this link solved the issue for me:

http://awesometoast.com/yosemite-core-storage-and-partition-woes/

 

[JGCox1214]

I have a single drive with two partitions.Can you tell me if I erase the Yosemite partition it want screw up the other partition?

Am I really out of luck if the diskutil cs list command indicates "no" for "revertible" under the bottom Logical Volume? Does anyone know of a way around it?


$ diskutil cs list

CoreStorage logical volume groups (2 found)

|

+-- Logical Volume Group FAAA96C6-8B05-4D27-93BE-A588559B0936

| =========================================================

| Name: WINDOWS HD

| Status: Online

| Size: 1019623182336 B (1.0 TB)

| Free Space: 4653056 B (4.7 MB)

| |

| +-< Physical Volume C1846B12-C2E3-4333-B091-EAF5F95A6301

| | ----------------------------------------------------

| | Index: 0

| | Disk: disk2s4

| | Status: Online

| | Size: 1019623182336 B (1.0 TB)

| |

| +-> Logical Volume Family E8CF2F1B-15FC-4EC0-AC7E-2A7D7B339706

| ----------------------------------------------------------

| Encryption Status: Unlocked

| Encryption Type: None

| Conversion Status: NoConversion

| Conversion Direction: -none-

| Has Encrypted Extents: No

| Fully Secure: No

| Passphrase Required: No

| |

| +-> Logical Volume 3ED059D7-120E-43EB-814C-5198C33FA965

| ---------------------------------------------------

| Disk: disk4

| Status: Online

| Size (Total): 1019266203648 B (1.0 TB)

| Conversion Progress: -none-

| Revertible: No

| LV Name: Install OS X Yosemite

| Volume Name: Install OS X Yosemite

| Content Hint: Apple_HFS

|

+-- Logical Volume Group 36569120-4CEE-442E-BFEA-1640E108D1E4

=========================================================

Name: Macintosh HD

Status: Online

Size: 1979974803456 B (2.0 TB)

Free Space: 11653120 B (11.7 MB)

|

+-< Physical Volume 8DE52331-813F-4891-8A8E-15281327D876

| ----------------------------------------------------

| Index: 0

| Disk: disk2s2

| Status: Online

| Size: 1979974803456 B (2.0 TB)

|

+-> Logical Volume Family 8810DB8C-DDED-4A9A-8B9D-D1799A170F92

----------------------------------------------------------

Encryption Status: Unlocked

Encryption Type: AES-XTS

Conversion Status: Converting

Conversion Direction: forward

Has Encrypted Extents: Yes

Fully Secure: No

Passphrase Required: Yes

|

+-> Logical Volume F6466635-ED27-4D24-94B3-F4F6E5A09268

---------------------------------------------------

Disk: disk5

Status: Online

Size (Total): 1979610824704 B (2.0 TB)

Conversion Progress: 14%

Revertible: No

LV Name: OS Ex Storage

Volume Name: OS Ex Storage

Content Hint: Apple_HFS

 

[Weaselboy]

If you are referring to disk4, you are correct. For whatever reason that is not revertible so you are stuck.

Looks like disk5 is in the middle of a FileVault encryption run.