[Info-vax] VMS QuickSpecs

[Stephen Hoffman]

On 2015-08-20 12:54:57 +0000, Dirk Munk said:

> Stephen Hoffman wrote:
>> On 2015-08-14 09:48:44 +0000, Dirk Munk said:
>> 
>>> No, IPFC is not at all for long distance interconnects. That would meen 
>>> you would have very long distance firbechannel interconnects.
>>> FCIP on the other hand is used to tunnel FC over long distance IP connections.
>> 
>> If you want to use a more expensive and more limited and 
>> harder-to-manage infrastructure in preference to a much faster and 
>> cheaper and more flexible one, I'm sure there are vendors that will 
>> happily accept your money.
> 
> Harder-to-manage? Have you ever managed an FC network? I have, It is 
> very easy. Create a zone, add both end point of the zone (server HBA 
> and storage port) and bingo, you're ready. The underlying FC network 
> does the rest, it is completely self-configuring. Setting up the 
> network itself is also very easy.

Yes, I've managed Fibre Channel.   (Wasn't that obvious?)

Can you manage IP over FC using IP tools?  No.

Can you use IP switches and routers?  No.

Can you use IP knowledge?  No.

Can you use existing Ethernet infrastructure and existing management 
tools?  No.

Can you use IP over FC everywhere, and avoid replicating infrastructure?   No.

Which means...  It's harder, and it's more expensive.

Oh, and then there's that the the FC user interfaces are, um, lacking.


>>> If you already have a fibrechannel infrastructure available, and if 
>>> your systems already have fibrechannel connections, then using IPFC 
>>> becomes a very different matter.
>> 
>> How many of those folks lack speedy Ethernet networks?
> 
> So what? the one doesn't exclude the other.

If cost and cabling and training is no factor, sure.

>>> IP over fibrechannel can not be routed. You always use zones in 
>>> fibrechannel. with IPFC a zone becomes a very effective, fast and 
>>> secure VPN.
>> 
>> What'd be called a VLAN on the Ethernet infrastructure.
> 
> Maybe, but FC has VLANs too.

Now we have more complexity and more cost and more training, and for no 
particularly obvious network benefits beyond the Ethernet that I 
already have.

>> When might FC have architected autoconfiguration and autodiscovery 
>> support, and protocols that can be routed?
> 
> I don't know, but I don't regard IPFC as an general ethernet 
> replacement. A typical use could be a connection between an application 
> server and a database server. Because of the huge default MTU (appr. 
> 64kB) and a maximum MTU of even 16MB with IPv6 (if I remember 
> correctly), the result of a database request often fits in one IP 
> packet. I don't have to explain to you that handling a packet takes a 
> lot of computing power, the size of the packet doesn't matter really. 
> You don't even need TCP, FC in itself already takes care of guaranteed 
> delivery.

So now I have to deal with some other protocol that's not TCP?  That 
lacks autodiscovery and autoconfiguration?

There'll still need to be a cluster communications port emulator driver 
either reworked or wholly written, as you're going to want clustering 
here, too.

> CI is indeed what I was thinking about too with IPFC. However in the 
> era client-server applications were not very common, these days they 
> are common. A dedicated very fast low latency FC link in such a setup 
> is not such a strange idea.

We'll clearly disagree then, as I see the addition of IP networking 
over Fibre Channel as a waste of time, effort and money for VSI, and 
not something that will be a big draw for the existing OpenVMS 
installed base nor for potential new deployments of OpenVMS.   If 
end-user costs and training and infrastructure duplication are no 
object and if development costs were low and wouldn't offset other 
support I'd rather see available and if Ethernet weren't already faster 
and far more ubiquitous — that's three very big ifs — then I might be 
more interested in this.   But given budgets and staff and time are not 
infinite resources, then support for more 10GbE and 40GbE Ethernet NICs 
and the 100GbE as they arrive — I'm already effectively required to 
have IP via Ethernet configuration in almost any environment, after all 
— and existing FC storage support updated for faster HBAs, maybe also 
InfiniBand support for high-end storage, and (much) faster networking 
networking stacks, now I see that as aiming OpenVMS forward, and rather 
more interesting.   IP over FC, not so much.



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