I have an external hard drive with two partitions, each one formatted as "OS X Extended (Journaled, Encrypted)". The second partition mounts and asks for a password, but the first one does not. The hard drive is 1TB, the first partition is 895GB and the second partition is 104GB.
This is the output from diskutil list
/dev/disk2 (external, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk2
1: EFI EFI 209.7 MB disk2s1
2: Apple_CoreStorage 895.1 GB disk2s2
3: Apple_CoreStorage Extra 104.7 GB disk2s3
4: Apple_Boot Boot OS X 134.2 MB disk2s4
/dev/disk3 (external, virtual):
#: TYPE NAME SIZE IDENTIFIER
0: Apple_HFSX Extra +104.4 GB disk3
Logical Volume on disk2s3
888F03E6-B0A4-4E12-BA48-1DD1D1C3ED48
Unlocked Encrypted
This is the output from sudo gpt -r show disk2
start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 6
40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
409640 1748305920 2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC
1748715560 2008
1748717568 204539864 3 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC
1953257432 262144 4 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
1953519576 7
1953519583 32 Sec GPT table
1953519615 1 Sec GPT header
This is the output from sudo gpt -r show disk2s2. (The partition which won't mount).
start size index contents
0 1748305920
This is the output from sudo gpt -r show disk2s3. (The partition which mounts).
start size index contents
0 204539864
This is the output from sudo fsck_cs -y disk2s2. (The partition which won't mount).
Executing fsck_cs (version 517.50.1)
** Checking volume
** disk2s2: Scan for Volume Headers
Invalid Volume Header @ 0: unsupported format
Invalid Volume Header @ 895132630528: invalid field value
** disk2s2 did not complete formatting as a CoreStorage volume
[Edit 1] Here is the output from diskutil cs list
CoreStorage logical volume groups (2 found)
+-- Logical Volume Group F99A19A9-A491-475F-8271-3601E6624322
| =========================================================
| Name: MAINOS
| Status: Online
| Size: 209200443392 B (209.2 GB)
| Free Space: 4681728 B (4.7 MB)
| |
| +-< Physical Volume BA4F401C-1E9E-4236-9244-18DECF7A0E9C
| | ----------------------------------------------------
| | Index: 0
| | Disk: disk0s2
| | Status: Online
| | Size: 209200443392 B (209.2 GB)
| |
| +-> Logical Volume Family 41D930F7-7256-47C2-A660-B217DF788D79
| ----------------------------------------------------------
| Encryption Type: AES-XTS
| Encryption Status: Unlocked
| Conversion Status: Complete
| High Level Queries: Fully Secure
| | Passphrase Required
| | Accepts New Users
| | Has Visible Users
| | Has Volume Key
| |
| +-> Logical Volume 7B8D4144-0957-4D2F-9B7B-6FF545C56555
| ---------------------------------------------------
| Disk: disk1
| Status: Online
| Size (Total): 208843440128 B (208.8 GB)
| Revertible: Yes (unlock and decryption required)
| LV Name: MAINOS
| Volume Name: MAINOS
| Content Hint: Apple_HFS
|
+-- Logical Volume Group C909C3EC-B2C7-4E5A-B5EF-A9D18E3CA594
=========================================================
Name: Extra
Status: Online
Size: 104724410368 B (104.7 GB)
Free Space: 1024000 B (1.0 MB)
|
+-< Physical Volume 628B789A-80D3-465E-A7CC-A5D45E57552D
| ----------------------------------------------------
| Index: 0
| Disk: disk2s3
| Status: Online
| Size: 104724410368 B (104.7 GB)
|
+-> Logical Volume Family BC19D010-6E0C-49F6-A6A7-92FF7DA5A972
----------------------------------------------------------
Encryption Type: AES-XTS
Encryption Status: Unlocked
Conversion Status: Complete
High Level Queries: Fully Secure
| Passphrase Required
| Accepts New Users
| Has Visible Users
| Has Volume Key
|
+-> Logical Volume 888F03E6-B0A4-4E12-BA48-1DD1D1C3ED48
---------------------------------------------------
Disk: disk3
Status: Online
Size (Total): 104371060736 B (104.4 GB)
Revertible: No
LV Name: Extra
Volume Name: Extra
Content Hint: Apple_HFSX
I believe the partition header is broken, but I'm unsure. It sounds similar to issues posted here and here. I don't know how to go about fixing this and getting that first partition to mount.
Best Answer
Your disk 2 doesn't even seem to have a name. It could be something simple - like the name accidentally deleted in Finder - or a serious inability of the OS to read the partition.
As you can't mount it without a name, I suppose it will also be difficult to change the name in Finder again, if that is the issue. Sometimes, a disk boots even if it has errors - did you try starting with the alt key? If it works, make sure to name the disk in Finder, preferably with the original name.
If that fails, first step is to save all data on the computer which you can still access.
If you have a backup of the data you can't access, the easiest solution is to delete the non-working partition and to restore it from the backup. Be aware that this involves a high risk of deleting the whole disk, deleting the wrong disk accidentally and so on. Not to mention that you permanently loose all data if your backup has issues. And you might get an unstable file system if there are still underlying issues.
If you have important data and no backups, you might want to consider professional data recovery. That costs some money, but the risk of accidentally loosing all through a wrong diskutil command or such is much lower.
If the data is wanted but not important enough to spend so much money on it, the next step is a disk repair app. You install it on a system on another disk (not just another partition) and let it do its magic. With a little bit of luck, all is at least fine enough for making a backup of the data before starting anew.
If there is any hardware issue at the root of your problem or coincidentally with your disk, anything you do, even if you make no mistakes, can end your disk (not just your partition).
If the disk repair app doesn't work or you don't want to spend the money, you may try a few terminal commands for renaming the partition. I'm not sure whether renaming works in terminal or whether this deletes the partition. And I'm not sure whether diskutil or diskutil cs commands are needed for that - try either, and preferably with the original name, if you remember it. A restart and it might or might not work.
I assume you already tried all repair options in Disk Utility and with the diskutil command. If renaming works but doesn't resolve the issue, try them again.
I don't see any more options right now.