Thanks for the quick reply.  I will read the article that you linked.

Although "user error" is always my first guess, it seems unlikely that twice in 
a row I mistakenly clicked on a button other than the one I intended, 
especially after messing up once.  And if I clicked on the button I intended, 
then I'm still confused because I'm sure I have done this many times before 
without a problem, though I suppose something in the OS could have changed 
recently.

Thanks again for responding.  Maybe the article you cited will provide the 
answer, though I have not had time to read it yet.  I really appreciate your 
willingness to help.

Gregg

On Nov 2, 2014, at 4:12 PM, Macs R We <[email protected]> wrote:

> From the symptoms, it sounds to me like you accidentally did something that 
> started the RAID (or other logical volume) process on that device.  Now it’s 
> waiting to be combined with other devices to make up a logical volume.
> 
> You may have to break out Terminal and dick with the “diskutil coreStorage” 
> suite in order to tell the system you want to revert it to an independent 
> volume.  As long as you don’t accidentally target the wrong drive with any of 
> the commands, it’s not dangerous.  I had to do this myself to roll my own 
> Fusion drive… and then unroll it again when the experiment failed miserably 
> ("Could not mount disk16 with name (null) after erase,” whatever the **** 
> that means).
> 
> This article may give you a basic power-user's understanding of how Logical 
> Volume Groups are structured, at least enough for you to do the task ahead of 
> you.
> 
> On Nov 2, 2014, at 1:52 PM, Dinse, Gregg (NIH/NIEHS) [C] 
> <[email protected]> wrote:
> 
>> Hi,
>> 
>> When I want to re-use a hard drive for a new purpose, I open Disk Utility 
>> and click the Partition tab.  Then I choose how many partitions I want, 
>> their sizes, and their names.  I don't know how I got into the habit of 
>> doing this next step, but next I click on the Erase tab and give the same 
>> disk name.  Today I did this and had problems, even though it has always 
>> worked fine in the past.  I am running 10.9.5 and the disks are inside a 
>> 2012 Mac Pro.
>> 
>> Typically in Disk Utility, each disk has a primary entry on the left of the 
>> main window, which gives the total size of the disk, the brand, and the 
>> model, such as "3 TB Seagate ST33000651AS".  And then each partition has its 
>> own line, which shows the name of the partition.  And lots of useful 
>> information is given at the bottom of the window.
>> 
>> Earlier today, I re-created a single partition on a 3-TB drive and gave it 
>> the name "Disk_1".  Then I erased the disk and gave it the same name 
>> (Disk_1).  This is when the trouble started.  At this point, both the main 
>> line and the indented line showed the same name (Disk_1), rather than the 
>> primary line showing something like "3 TB Seagate ST33000651AS".
>> 
>> Also, when the primary line is selected, the bottom of the window shows 0 
>> Bytes available and 3 TB used, even though that is not the case.  If I click 
>> on the indented line, it says 2.99 TB available and 10 GB used, which sounds 
>> right.  Also, when I click on the primary line, the Type is listed as 
>> Logical Volume Group rather than something like SATA Internal.
>> 
>> I have tried to repair the disk, but this does not help.  I don't see any 
>> errors, though the listing is longer than usual.  When I select the primary 
>> line, I only get 2 tabs (First Aid and Partition) rather than the usual 5 
>> tabs (First Aid, Erase, Partition, RAID, Restore).  And if I click on 
>> Partition, everything is greyed out -- I can't choose a new partition 
>> layout, or name, or size, nor can I click on the Options button or the 
>> Revert button.
>> 
>> I do not think the disk itself is bad (or at least not before I started 
>> mucking with it), so I tried a second disk and had even worse results.  I 
>> wondered if the name "Disk_1" was a bad choice, since perhaps it is reserved 
>> for use by the system (though if so, I would hope the system would warn me 
>> not to use that name).  So I called this one HD_2.  This time, when things 
>> looked to be going bad in the same way, I clicked on a Cancel button, hoping 
>> to prevent the same problem.  But this must have made a worse mess.  Now I 
>> only have a main entry, and again it says "HD_2" rather than something like 
>> "3 TB Seagate ST33000651AS".  Also, it again says "Logical Volume Group" 
>> rather than SATA Internal.  And there is no second, indented line!  As 
>> before, there are only 2 tabs rather than 5.  And if I click on the 
>> Partition tab, everything is greyed out, so I can't do anything.
>> 
>> What have I done?  Is there some way to fix my disks?  I tried copying a 
>> large file to Disk_1 and it seemed to work.  But something sure seems messed 
>> up.  And I don't know how to rename or repartition these disks.  I sure 
>> don't trust them in their current state.
>> 
>> By the way, somewhere in this process I remember seeing a message about an 
>> encrypted disk, but I did not intentially do anything with encryption (now 
>> or ever).  I don't know if that is related.
>> 
>> Any help would be very much appreciated!  Thanks in advance,
>> 
>> Gregg

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