[Info-vax] Volume shadowing and current SCSI standards ?

[Mark Berryman]

On 4/29/22 9:25 AM, Phillip Helbig (undress to reply) wrote:
> In article <68f2137f-d0e6-4921-98ee-854022f7d751n at googlegroups.com>,
> abrsvc <dansabrservices at yahoo.com> writes:
> 
>> The current HBS product requires the use of the READ/WRITE LONG commands
>> so you are correct HBS won't work with devices that don't support it.
>> Many customers now use SAN devices and the "shadowing" takes place there
>> rather than being host based which avoids the issue. I have seen the
>> shift with many of my clients to this "new" way.  Yes HBS is valuable
>> for many reasons, but there are alternatives that are increasingly being
>> used today.  While this should be addressed, I don't think it has the
>> urgency that you incidate.
> 
> Merely the fact that most don't expect such an essential feature to
> break should be reason to address it.

Read/Write Long was marked obsolete more than a decade ago.  Thus, I 
would think that if it had a negative impact on any of VSI's customers, 
they would have let VSI know.

> 
> SAN?  Yes, can provide help if a disk fails.  But what about multi-site
> clusters with members with physical connections to different nodes?

Multi-site clusters are actually one of the strengths of SAN.  SAN 
protocols support long distances much better than the SCS protocol does. 
  In fact, I wonder if it would be practical (or possible) to eventually 
run cluster traffic over fibre channel.

> 
> And what about HBVS on hobbyist machines?  :-)
> 

I realize you asked this tongue-in-cheek but hobbyists tend to get most 
of their equipment on the used market.  The used market still has plenty 
of stuff that still supports Read/Write Long.

Mark Berryman