Shadowing question

[Wim Van den Wyngaert]

Starting from what VMS version can I mount a shadow disk of 2 GB consisting of a disk of 2 GB and a disk of 4 GB ?

And I seem to have lost the link to what changed in all VMS versions (the history of VMS). Someone knows where to find it ?

Wim

[EdgarZamora_1]

From google:

Starting with V7.3-2, Volume Shadowing allows shadow sets to contain devices of differing size and geometry (Dissimilar Device Shadowing). Combined with the feature allowing Dynamic Volume Expansion, a shadow set can now be grown "on the fly" without bringing down the entire shadow set.

[Wim Van den Wyngaert]

Edgar,

Could be, but before that, were 2 members of different size not allowed to live together (with the size of the smallest ?).

Wim

[Duncan Morris]

Wim,

I think that Edgar is correct with his version.

From an old Ask the Wizard......

Disk devices -- whether dissimilar or otherwise -- can now be shadowed using host-based OpenVMS Volume Shadowing, so long as all disks involved in the shadow set have the same total number of blocks.

Support for shadowing disks with differing numbers of total blocks is under discussion for an OpenVMS release -- currently a release after the (not available at the time of this wiring) OpenVMS V7.3 release.


Duncan

[Duncan Morris]

Wim,

confirmed from the V7.3-2 volume shadowing docs:-

Starting with OpenVMS Alpha Version 7.3-2, different size devices can be used to form a shadow set. This functionality is called dissimilar device shadowing (DDS). To use DDS, all systems that have mounted a shadow set whose members differ in size must be running OpenVMS Alpha Version 7.3-2.

Prior to OpenVMS Alpha Version 7.3-2, Volume Shadowing for OpenVMS required that all members of a shadow set be the same size, that is, that each member have the exact same number of blocks. The rapid advance of disk technology has made this requirement impractical. The flexibility of using different size devices outweighs the space that will be unused on the larger device.

Duncan

[Volker Halle · Accepted solution]

Wim,

here is the OpenVMS Release History link:

http://h71000.www7.hp.com/openvms/os/openvms-release-history.html

It is not always detailled enough, but it shows the major enhancements.

Volker.