[Info-vax] Kittson question

[Stanley F. Quayle]

On Thursday, January 1, 2015 6:28:08 PM UTC-5, JF Mezei wrote:
> When a remote disk is served vis MSCP, does the local host use any
> driver specific to that remote disk or does it use a vanilla MSCP driver
> to access the disk ?

The host system doesn't "speak" MSCP; VMS does it across the network, just like a physical VAX does.

> From a technical point of view, would an application ever see a
> difference ?  Would this generally result in the "fake" DSSI traffic
> traveling on a separate ethernet link from SCS so that you could have
> those on separate ethernets to provide some redundancy ?

You can have multiple network adapters (just like a physical VAX), and VMS will use them all. Unless you configure a DEQNA on later versions of VMS, but that's a VMS issue, not a CHARON one.

> is there a point in emulating more than one disk device type ?

Some customers have VAXELN applications running on CHARON-VAX. I'm not sure if VAXELN cares. Anyone know?

> are you able to pass the SCSI commands directly to the hardware ?

We can and do. CHARON-VAX can either use the Windows device name (\\.\PhysicalDriveXYZ) if the disk has a Windows driver, or direct SCSI commands to the device, bypassing Windows.

> The way I see it: when VAX was alive, people upgraded from one VAX to
> the next.

The point is that many of these customers don't want to UPGRADE, just use modern hardware -- which does not exist for a VAX, or an early Alpha.

> But define/system/exec DUA0 DKA200  works too in trying to provide
> transparent move to a new system.

Actually, the command is "define/system/exec DUA0 DKA200:" -- you need the colon to make it work. :-)

I've used that trick many times in the past. But the latest versions of CHARON-VAX allow you to configure the device names so that they look like the physical ones.