Different UUIDs for the same partition?

[nontroppo]

Hi, Yosemite seems to convert boot partitions into CoreStorage volumes, and my main root volume has 2 different UUIDs when I check via diskutil or "Get Info" in Disk Utility:

I thought the idea of the UUID was that it was Universally Unique? Perhaps this is an issue with Disk Utility?

Do other users see two different UUIDs for their main boot volume?

Also my Recovery HD is not accessible when I use [option] on a reboot (though of course ⌘R works), is that normal for Yosemite (perhaps this has been hidden for a while)?

 

[Weaselboy]

Hi, Yosemite seems to convert boot partitions into CoreStorage volumes, and my main root volume has 2 different UUIDs when I check via diskutil or "Get Info" in Disk Utility:

I thought the idea of the UUID was that it was Universally Unique? Perhaps this is an issue with Disk Utility?

Do other users see two different UUIDs for their main boot volume?

What you are seeing is normal and you are not seeing what you think.

That info screen from Disk Util is the hardware UUID for your drive and is hard coded into the drive itself. It will never change.

Those UUIDs you are seeing in Terminal are all made up by the OS when creating the core storage volume.

Go to Apple menu then About this Mac then System Report and scroll down to the Storage section on the left and click it. In there you will see the volume UUID for the hard drive (disk1 hardware UUID) that will match the one in Disk Util. Below that you will see the UUIDs for the logical volumes the OS assigned.

Also my Recovery HD is not accessible when I use [option] on a reboot (though of course ⌘R works), is that normal for Yosemite (perhaps this has been hidden for a while)?

Yeah... that seems to be new with Yosemite and I have seen others report the same thing.

 

[mikecwest]

Hi, Yosemite seems to convert boot partitions into CoreStorage volumes, and my main root volume has 2 different UUIDs when I check via diskutil or "Get Info" in Disk Utility:

Image

I thought the idea of the UUID was that it was Universally Unique? Perhaps this is an issue with Disk Utility?

Do other users see two different UUIDs for their main boot volume?

Also my Recovery HD is not accessible when I use [option] on a reboot (though of course ⌘R works), is that normal for Yosemite (perhaps this has been hidden for a while)?

if you don't want the storage to be like that, just revert it.


I am not an expert, but I believe you need to open terminal and type:

diskutil coreStorage revert disk1

If that does not work, try this post:

https://forums.macrumors.com/posts/19350462/

If needed:

You can see more details here:

https://forums.macrumors.com/threads/1741742/

 

[Weaselboy]

if you don't want the storage to be like that, just revert it.


I am not an expert, but I believe you need to open terminal and type:

diskutil coreStorage revert disk1

If that does not work, try this post:

https://forums.macrumors.com/posts/19350462/

If needed:

You can see more details here:

https://forums.macrumors.com/threads/1741742/

Yes, this command (with the real UUID) will revert the core storage volume. I have been wondering if there is a reason Yosemite does this though and if one would be better off leaving it alone? It does not seem to harm anything.

It would have been nice if Apple put something out explaining why this was done. I have seen no explanation for it.

diskutil coreStorage revert UUID

 

[mikecwest]

Yes, this command (with the real UUID) will revert the core storage volume. I have been wondering if there is a reason Yosemite does this though and if one would be better off leaving it alone? It does not seem to harm anything.

It would have been nice if Apple put something out explaining why this was done. I have seen no explanation for it.

diskutil coreStorage revert UUID

I did it with the volume id "disk 1" instead of the UUID.

If we discover that there is an advantage to having it as corestorage, all we have to do is go back to terminal and type:

diskutil CoreStorage convert UUID

or as I used

diskutil CoreStorage revert disk01s2

 

[nontroppo]

Thanks to you both for your informative answers! I'm happy to stick to CoreStorage for the moment...

Indeed, there has been some speculation on why Apple are moving over to using CoreStorage as the default.

There is some valuable info on the following several posts too:

http://blog.fosketts.net/2012/10/03/mac-os-corestorage-tricks/
http://blog.fosketts.net/2011/08/05/undocumented-corestorage-commands/

There was some surprise when Apple released CoreStorage with Lion as it seemed an over-engineered solution just to enable disk-wide encryption, the hope was this was to grow feature-wise. And Fusion drives were one result. But the fact Apple are only now switching this as the default may suggest some other features coming soon?

I hope Disk Utility will be updated to better handle CoreStorage features, before Yosemite goes gold...


As an aside, if you look as my screenshot you'll see my root logical-volume-group has 2.8GB free space -- I've seen this exact value on another persons 'diskutil cs list' -- Is this really unused space or somewhere where the Recovery and EFI partitions live (unlikely as the physical volume disk0s2 is large enough (499GB) to house them), or perhaps this is SSD provisioning (unlikely as I thought that was firmware controlled below the BSD level)???

 

[campyguy]

nontroppo, I read your latest post with some interest, having dealt with the first and latest DP installers creating LVGs. I installed the DP5 on my internal SSD, and an LVG was created, and on an external SSD, and a non-LVG with two partitions were created. The DP1 installer created LVGs on each SSD devices. The change in formatting results between DP1 and DP5 leads me to think that Apple is "working on it" - whatever that means...

I'm not sold on Logical Volumes, and IMO Apple's not including LVG management in Disk Utility (to this point) IMO suggests to me LVG creation for partitioned single drives (especially system drives) is unintended - read: a bug.

There's been some posting in these forums that there may be no harm/disadvantages to the creation of LVGs on single-volume system drives created by the Yosemite DPs. I talked with my IT person, he referred me to what's offered on Wikipedia: https://en.wikipedia.org/wiki/Logical_volume_management#Disadvantages - and likened (not literally) LVGs to RAID0, as in one drive fails, they all fail and data recovery is the next step - a PIMA. We use RAID10 - redundant RAID0 setups, just to be proactive, and Yosemite's LVG creation of internal drives gives me pause.

Dynamic resizing of partitions would be nice - however, there's nothing in Apple's documentation of Yosemite that indicates or addresses LVG creation on single drives; it's all targeted to Fusion Drives. That Disk Utility still does not address how to fix/adjust/delete this - generically - but Terminal does, IMHO this is still to be viewed as a bug, and caution is to be used in this instance.

I am still reverting single-drive LVGs created by Yosemite. But, that's just me writing. I'd love to be *proven* otherwise. I've reached out to Apple Engineering, but haven't received a serious response.

 

[Weaselboy]

I did it with the volume id "disk 1" instead of the UUID.

If we discover that there is an advantage to having it as corestorage, all we have to do is go back to terminal and type:

diskutil CoreStorage convert UUID

or as I used

diskutil CoreStorage revert disk01s2

Thanks for this. I saw a report from a user who spoke with an Apple engineer who told him this would work also as long as you wanted to revert all volumes mounted. Have not tested it though. Makes sense it would work though.

diskutil CoreStorage revert /

 

[nontroppo]

Because CoreStorage was introduced with Lion and both FileVault2 and Fusion Drives depend on it, I'd imagine this is a robust technology (if anything Apple does with filesystems and storage could be called robust!!!). I'd also imagine Apple didn't "accidentally" convert all drives to use it in a public beta, that this is intentional; we just don't know why. Anyway because converting is non-destructive I doubt those who've reverted and those who've left it in place need to worry too much...

Some additional reading, Siracusa's Lion review page on CoreStorage from 3 years ago:

http://arstechnica.com/apple/2011/07/mac-os-x-10-7/13/

Boy when you look at the wonderfully detailed XCode / Swift changelogs, one **really** wishes the OS X team would learn the value of the changelog, having something of the scope of autoconverting disk partition structures without any developer/beta tester info at WWDC or anywhere else is infuriating...