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VCM\VCEM questions

Trusted Contributor

VCM\VCEM questions

Here are some questions that came from a customer looking at Muti-Enclosure Stacking and managing the Virtual Connect Domains. Maybe you have some of the same questions.


Q1. If one chassis fails, is the chassis information (from the domain) available to another chassis??  Where is it stored?

Ans1. MES or VCEM ? In a MES domain, the configuration is stored in the VC modules in bays 1&2 of the base enclosure. If you lose both modules, you lose the capability to make any configuration changes until you bring them back. You do not lose I/O in the other enclosures of the domain (unless all your uplinks are off the modules that are down of course). In a VCEM domain group, the configuration is stored in the CMS database.


Q2. Exactly how does a chassis fail to another chassis under VCEM?

Ans2. A chassis does not fail to another chassis under VCEM. A chassis does not fail to begin with ;-) A server in a chassis can failover to a server in another chassis. That’s just VCEM moving the server profile from the failed server to the spare one.


Q3. How many chassis are in a domain under VCEM?

Ans3. Whoa, let’s not confuse terminology. “Domain” is a Virtual Connect term, so is MES domain for multi-enclosure stacking. MES and VCEM have NOTHING to do with each other. You can have a domain, including a MES domain, with or without VCEM. You can have VCEM with or without MES. A MES domain can have up to four enclosures, yes. What VCEM brings is “domain groups”, a VCEM domain group can have up to 250 VC domains. Each of these domains can (but does not have to) contain up to 4 enclosures if you use MES, so you could go up to 1000 enclosures in VCEM.


Comments or other questions?


Re: VCM\VCEM questions

Yes i have other questions. I have deleted my original post as this seem to be a good thread to go a bit further in this matter. I rephrased my original post with new terminology (like MES for a multi-enclosure stack):




1) Can i create one VC Domain (for example: VC_Domain_A) and then add 3 standalone enclosures to it ?

2) How many single enclosures can i add to the same VC domain like this ? 4 ? And is this a supported configuration ?

3) It is VCM that is responsible for replicating the config to all 'remote' enclosures. Is this done using the OA connection ?

  3b) Do all the enclosures need to be in the same OA vlan for this ? Or can the OAs be in seperate VLANs ?

      I have read that in a MES all enclosures need to be in the same OA VLAN. But is this also true in a VC

      domain made up of different standalone enclosures ?

  3c) Do the 'remote' enclosures also contain a complete configuration ? (ie what happens if the primary enclosure -the one that was first "up" in the domain fails ? The other enclosures can continue with their configuration ?


4) What if i replace in the example above a physical enclosure by a MES enclosure (with 3 members) for example ?

Can i still add 4 of these to the same VC domain ? (This domain would then be composed of 12 enclosures: 4 stacked enclosures, each with 3 members ?


5) What are the constraints in such a domain ?

     5a) For example: do the LAN & SAN uplinks need to be in the same position in each enclosure ?

     5b) Do i need to use the same VC switches in this domain ? I assume i cannot mix Flex-10 and VC1/10-F modules in such a domain ?

     5c) If i stack one enclosure, do i need to stack all the other enclosures ? Can one physical enclosure be standalone and another part of the domain be a dual-stacked MES enclosure ? I understand there must be some limitations here.


6) What is the use of creating Domain Groups in VCEM then ? Only the MAC management ? And 'spare' capability ?


If i create a VCEM Domain Group composed of different VC Domains, do i still have the same limitations as in point 5 ? Or can my individual VC Domains be composed of more "diverse" hardware since VCEM does not do replication of VCM domain config ? Does VCEM enforce restriction/conditions on the VC Domains that are inserted in the same VCEM Domain group ?