[Info-vax] New filesystem mentioned

[Bob Gezelter]

On Wednesday, May 15, 2019 at 1:41:34 PM UTC-4, Bob Koehler wrote:
> In article <qbf9r5$9f4$1 at dont-email.me>, Chris Scheers <chris at applied-synergy.com> writes:
> > 
> > There were file systems in VMS before clusters and those file systems 
> > still work.
> 
>    Files-11 ODS-1 and Files-11 ODS-2 existed before clusters.  ODS-1
>    is only suppoted on VAXen, and I don't know if it has cluster
>    support.
> 
>    ODS-2 supports clustering because VMS Engineering put the DLM
>    calls into the ODS-2 code.
> > 
> > For example, it should be possible to side step the DLM by doing a 
> > local, ACP based file system and MSCP serving the results to the cluster.
> 
>    MSCP serving is DLM based.

Bob,

A point of order.

ODS-1 and ODS-2 are specifications for on-disk file structures (hence the acronym). If memory serves, both were originally written for RSX-11 family operating systems, before the VAX/VMS project. Early copies of the ODS-2 specification had field names conforming to MACRO-11 conventions/requirements.

Support for ODS-2 was first realized (at least as a product), in VAX/VMS. It is the default file system format at first deployment. ODS-1 was also supported, with the goal of being able to mount RSX-11 volumes on VAX/VMS.

The code bases for the VAX/VMS ACPs implementing ODS-1 and ODS-2 are implementations of the respective specifications (there are also features which appeared in the specifications which were not implemented in the VAX/VMS ACPs. (ODS-5 is an enhancement to ODS-2).

The XQP implementation of ODS-2 first appeared in VAX/VMS 3.3. 

If I recall the timeline correctly, the DLM appeared in VAX/VMS 4.0, as part of the VAXcluster support.

It is important to differentiate between a specification and an implementation of a specifcation. There is nothing in ODS-2 or ODS-5 about OpenVMSclusters, the issues do not effect the contents of the disk data structures.

The details of locking resources between cluster members does require support within the implementation, namely the XQP.

- Bob Gezelter, http://www.rlgsc.com