Managers - Confused!

[Paul Hutchings]

Thanks Mark, I know you can use basic player or whatever they call it now for the FOM, I was just thinking out loud I guess over whether there is any point running it somewhere other than on local storage on one of your vSphere hosts.

[Paul Hutchings]

Incidentally, if I had a FOM in Site A, would I still bother to designate Site A as "Primary" in the CMC?

I'm thinking what if I temporarily lose Site A and wanted the P4000 in Site B to take quorum but not permanently as the manual suggests the "Recover Quorum" command would do.

[teledata]

Since you have additional nodes available, I would not bother with the FOM, but just run the 5th manager on one of your other nodes at the primary location...

FOM was introduced to solve the original problem of requiring a customer to buy at least 3 nodes to create a high availability cluster.

Since you already have additional SAN/iQ nodes available in your management group, there isn't any benefit (that I can see) to using FOM over one of your existing nodes.

[Paul Hutchings]

"Since you have additional nodes available, I would not bother with the FOM, but just run the 5th manager on one of your other nodes at the primary location..."

Yes I was thinking about this and I'm less and less keen on the FOM as it seems to assume my primary site will always be available, and whilst it makes a link failure easy to deal with, it seems it makes a loss of Site A tricky to deal with.

Would I be correct in thinking the following is sensible?

Run regular 3 managers in Site A, and 2 regular managers in site B.

Link dies - A has Quorum.

B dies, A has Quorum.

A dies, split brain so bring up a VM in site B to regain quorum.

[teledata]

You've got it... Or (as in your other recent post) you can do your 3rd site to get the best of all worlds...

The only thing that bothers me about the 3rd site, is if site A looses all network connectivity you are down..

I would keep an offline mirror of your FOM that normally is running at the 3rd site, so if you loose all links you can launch the "copy" of your FOM to regain SITE A functionality if needed.

[Paul Hutchings]

Yeah I did think about taking a snapshot/cloning the FOM but I didn't know if it would work - I figured if I tried it during a testing period it may not reflect any "Get lost I don't know who you are" that might occur a year down the line if I suddenly bring up a cloned FOM.

Tbh even ignoring the FOM issue, I'll sleep much better with a third switch and redundant network topology - really I think I stuffed up not planning that from the outset but those Proliant Microserver's are cheaper than a PC to just run the FOM.

As for HP's SFP/GBIC pricing however......

[Terry.giblin]

Quorum:

At least 3 or 5 'nodes' to create a high availability cluster.

That's what it said on the box, in my garage.

If only, it was that simple.

30 years of VMS.

[teledata]

Since you are running your FOM as a virtual machine, you could pretty easily use VCB or periodically shut it down, and take an updated snapshot or copy of the FOM disk files...

You could even automate it with a script ie:

Sunday 3am, shutdown FOM
Copy disk files over WAN
restart FOM

[Paul Hutchings]

Yeah I may look into that.

Presumably if you lose all three sites in different order due to, say, power or "something bad", but you they all come back (at different times as power is restored) quorum takes care of taking the cluster offline, then when things come back there's a resync/quorum is restored?

I can only test so much with yanking cables...

[Terry.giblin]

"I can only test so much with yanking cables..."

How long can an 'ethernet cable' be?