[Info-vax] Error using fibre channel target on FreeBSD from OpenVMS

[Matthew R. Wilson]

On 2022-04-28, John Wallace <johnwallace4 at yahoo.co.uk> wrote:
> On Thursday, 28 April 2022 at 10:02:56 UTC+1, Matthew R. Wilson wrote:
>> VMS was repeatedly issuing READ LONG(10) commands (operation code
>> 0x3e), and it looks like FreeBSD hasn't implemented that command. In
>> the source, I see it's just stubbed out to always return an illegal
>> request check condition. 
>> 
>> At least the problem is clear. I'll have to look into what it takes
>> to implement support for the READ LONG(10) command, and see what
>> command(s), if any, it gets stuck on next. 
>
> READL (aka "read long") and the equivalent write command are important
> parts of VMS volume shadowing - so important they're even mentioned in
> the Software Product Description. Have a read (if you haven't already
> done so), see if it helps you work out what's going on, and whether it
> matters for your needs or not.
>
> E.g. this is one snippet from the VSIVMS Volume Shadowing Guide at
> e.g. https://vmssoftware.com/docs/VSI_VOLUME_SHAD_GD.pdf section 1.3.2
> Supported Devices:

Interesting. The wording in the Volume Shadowing Guide seem to imply
that VMS itself would work with devices that don't support READ/WRITE
LONG, but you shouldn't use them with Volume Shadowing.

It seems like for FC devices, the support isn't optional. That may make
sense knowing how important it is for Volume Shadowing... due to the
fact that FC targets are often available via multiple paths and are
likely shared between different systems, the same reasons Volume
Shadowing depends on READ/WRITE LONG may be relevant for the common FC
configurations.

The READ LONG and WRITE LONG commands have been removed from the latest
SCSI standard. I wonder if that's why VMS refused to try to work with my
target when it was reporting that it was a version SPC-5
implementation... VMS may know the READ/WRITE LONG commands are no
longer in the standard and so rejects the new version. (Or it may have
no special knowledge of SPC-5 and later at all, and just plays it safe
and refuses it because it only knows about SPC-4 and below.)

Thanks,
Matthew