[Info-vax] Distributed Applications, Hashgraph, Automation

[Richard Maher]

On 16-Feb-18 11:15 AM, Kerry Main wrote:
>> -----Original Message-----
>> From: Info-vax [mailto:info-vax-bounces at rbnsn.com] On Behalf Of
>> Richard Maher via Info-vax
>> Sent: February 15, 2018 9:20 PM
>> To: info-vax at rbnsn.com
>> Cc: Richard Maher <maher_rjSPAMLESS at hotmail.com>
>> Subject: Re: [Info-vax] Distributed Applications, Hashgraph,
> Automation
>>
>> On 15-Feb-18 8:17 PM, Kerry Main wrote:
>>>
>>> Just to clarify -
>>>
>>> While the OpenVMS community refer to its clustering arch as shared
>>> everything, the industry term for the same thing is shared disk.
>>>
>>> In both cases, one could refer to these as differing strategies to
> share
>>> data between multiple systems. There are pro's and con's.
>>>
>>
>> I disagree and think you'll find that the third option "shared
>> everything" includes share memory. I can't believe I've forgotten what
>> VMS' offering for a low latency interconnect was Memory Channel?
>>
>> Oracle Cache Fusion and Redis Cache are wide area examples.
> 
> mmmm.. it's a bit different, but the basics are really about how data
> sharing is done between servers.

IMHO Share Everything does what it says on the tin.

> 
> Regardless of whether disk or memory sharing, with shared disk (OpenVMS
> - shared everything), there is still a DLM doing the inter-server update
> coordination.

And Oracle took that beautiful tool with its bullshit 16 then 64? byte 
LVB limitation and create Cache Fusion where the data moves around the 
cluster WITH the lock and so much i/o is simply eliminated.

VMS engineering asleep again with their head up their arse about 
DECforms :-(

> 
> I fully agree OpenVMS has significant advantages over other shared disk
> offerings - mission critical proven DLM, cluster logicals, cluster
> batch, common file system (new one with significant new features cooking
> as well). However, the industry really only looks at shared disk or
> shared nothing.

It also has many disadvantages: -
1) Maximum number of nodes
2) Geographical limitations
3) No PaaS capability

> 
> Btw, the modern day equivalent to memory channel and ultra low latency
> data sharing is either Infiniband or RoCEv2 (RDMA over converged
> ethernet)
> 
> Not sure where it is at right now, but RoCEv2 is on the research slide
> of the OpenVMS roadmap.

Goodo.

> 
> Imho, this type of cluster communications capability is critical to next
> generation cluster scalability of shared disk clusters.  It is how VSI
> can address the biggest counter argument to shared disk clusters -
> "shared disk clusters have scalability issues due to the requirement of
> a distributed lock manager"

Oracle's DLM seems not to have these scalability issues.