Was /CRC always in OpenVMS BACKUP command?

[Uwe Zessin]

> That looks a lot like the argument I have been getting for about 10 years on minimerge'

Well, that _is_ the argument. No WHL in the SCSI devices and the existing VMS software could not do mini-merges.

Compaq even spent time to implement history logging in the HSG controller's firmware, but when it was almost ready for release the product became End-Of-Life.

[Robert Brooks_1]

Uwe wrote . . .

Compaq even spent time to implement history logging in the HSG controller's firmware, but when it was almost ready for release the product became End-Of-Life.

----

Not quite correct. The HSG80-with-WHL capability was never "almost ready for release". At the time when that project was
halted, we were at least 9-12 months away from shipping a finished product. Before that development effort was scrubbed, the HSG80 had already been declared at end-of-life, but we were still planning on releasing the HSG80 firmware change *after*
the EOL designation.

The WHL implementation on the HSG80 differed
significantly from the WLG implementation
on the MSCP-speaking controllers. A key difference is that the write history logging
was kept on the members of the shadow set itself, not inside the controller. We discovered rather late in the development of WHL that this created some theoretical synchronisation issues that were nearly impossible to solve.

After an extensive review of the WHL design,
we decided to start from scratch with HBMM.

Given that WHL would not have ever been extended to any of the new controllers (EVA, etc...), we are pleased that the HBMM
solution is controller-independent!


-- Rob

[Uwe Zessin]

Now, that is interesting, because:

take a look at document EK-G80CL-RA.B01 (HSG80 Array Controller V8.7 Command Line Interface Reference Guide) - for example: on page 54, which describes the "ADD UNIT" command:
""WRITE_LOG
NOWRITE_LOG (default)

Marks the defined unit as an OpenVMS Host Based Volume Shadowing shadow set member.

IMPORTANT: This switch is only supported with ACS version 8.7R or version 8.7W code. NOTE: The specified unit is only marked and not enabled.

To enable a unit as an OpenVMS Host Based Volume Shadowing shadow set member, a single controller or both controllers of a dual redundant pair must be restarted. During the restart, the additional memory structures required for GWHL are allocated and initialized. Once enabled, the unit can only be disabled as an OpenVMS Host Based Volume Shadowing shadow set member by use of the NOWRITE_LOG command. When the log unit is disabled, it is not necessary to restart the controllers - this needs to be done only when a log unit is enabled. Log units can be JBODs, stripesets, RAIDsets, or mirrorsets. However, this unit cannot be a member of a Snapshot or Remote Copy set.
...""

To me, that looked like the product was almost ready ;-)
Thanks for the update, anyway.

[Robert Brooks_1]

To me, that looked like the product was almost ready ;-)

----

Oh yes, I agree -- the ACS software was certainly near release. It was the work within the shadowing driver that still had a long way to go.

-- Rob