SAN Basics

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Dave Smif
New Member

SAN Basics


I'm looking to get an HP2012fc DC MSA with an HP StorageWorks 4/8 Base SAN switch for use in a VMWare ESX Vi environment and have a couple of basic questions that maybe someone can help with?

I've read (on this forum) that it appears to be "the done thing" to use two switches with a DC MSA and was wondering on the reasoning behind this? Is it just for switch failure? Do they fail often?

If I was to get two switches, would two SW 4/8 Base SAN switches work or would I need different models? I've been reading the docs and I'm not sure if they work in a redundant setup?

Last and not least, I'm looking to backup the MSA. Ideally I'd like an active/passive setup, but am not really sure how to approach that. Can the 2012fc DC be used in this way? Would I need extra licences? If I was to just use one SAN, could I create snapshotable (I think I just invented a word) volumes that would allow me to easily backup live VMFS volumes?

Uwe Zessin
Honored Contributor

Re: SAN Basics

Those switches are pretty reliable - I still have two 1 GBit switches from 2000:
fcswa1:admin> uptime
Up for: 814 days, 13:07
Powered for: 2583 days, 6:45
Last up at: Mon Aug 14 08:43:50 2006

More often a power line goes off or needs maintenance - for which I like to see redundant power-inlets even on base switches. Two switches allow for two different management domains - for example, a zoning error in one fabric will not kill everything.

You can use 2 base switches without problems in a small environment. They don't even need a Fabric license, because they should not be interconnected anyway. The MSA2000fc and a server with two FC ports allow for a fully redundant setup.

The MSA2012fc dual controller model work with its own interpretation of active/active:

- a single virtual disk (vdisk) is managed by one controller and all the volumes contained in the vdisk can be presented in an active/active fashion to both controller ports (which should be connected to two different FC switches).

- another virtual disk can be managed by the second controller and the same rules apply.

You can create controller-based snapshots but how do you ensure data integrity / consistency?