[Info-vax] questions on initialize/gpt

[Stephen Hoffman]

On 2015-06-21 13:54:31 +0000, Dirk Munk said:

> I just read the chapter on the DCL initialize command,

Go read <http://labs.hoffmanlabs.com/node/209> and 
<http://labs.hoffmanlabs.com/node/112> for an intro, and then 
<http://labs.hoffmanlabs.com/node/28> for far more details on the 
low-level structures and organization.

>  and there it says:
> 
>  >> When /GPT is specified, the system file [000000]GPT.SYS is created. 
> GPT.SYS contains partition/boot information needed by the IA64 console 
> software. (GPT is an abbreviation for GUID Partition Table, where GUID 
> stands for Global Unique Identifier.) <<
> 
> That seems to suggest the disk gets a industry standard GUID Partition 
> Table, or not?

Yes.  The ODS-2/5 GPT.SYS file "protects" the GPT structures; it 
overlays the structures.   Other ODS-2/5 files are used to "protect" 
other partitions that can be present, as well.

> But then you would expect to be able to take a partition on an existing 
>   disk with a GPT label, and format it with ODS-2 or ODS-5, but I can't 
> find any information on that.
> 
> What is going on here?

What's going on is that ODS-2 and ODS-5 are overlaid across the entire 
disk including across the GUID partition table (GPT) data structures at 
the front (low-numbered sector addresses) and back (high addresses) of 
the disk, centrally because the OpenVMS bootstrap and the OpenVMS 
device drivers and some associated and ancillary pieces such as MOUNT 
do not support disk partitioning.

This has been discussed several times before, of course.

I'd hope that VSI would implement partitioning support at some point, 
but they've not discussed it.


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