As a reference to anyone watching, an engineer at Cisco addressed my question about the meaning of "adjacency". He stated, "The question to ask, is do the VSANs exist on the same switch where you have the IVR feature? In your case, both VSANs are on the same switch and are adjacent. For example, if you had two switches, one with SAN 5 and 20, the other with 10 and 20, where only 20 is allowed over the ISL, the adjacent VSANs would be 5,20 on the first switch and 10,20 on the second switch. VSANs 5 and 10 are not adjacent."
With respect to my need for a transit VSAN in the above scenario, he said the following:
- "No transit VSAN is required in your scenario. Creating a "Transit" vsan in this situation would not increase the robustness of IVR."
...And about the general use of transit VSANs:
- "In general, the simpler the better. Especially with IVR. If you can reduce the number of IVR enabled switches, and the number of VSANs, this will normally make troubleshooting easier.
Since there is only one IVR zoneset in a fabric, all VSANs and transit VSANs will participate in the IVR topology on that fabric. The fewest number of transit VSANs will result in a simpler design and make it easier to troubleshoot.
Transit VSANs have the most benefit when you are creating a IVR topology over a WAN (FCIP or Optical for example) that may be potentially unreliable (rare now a days) that is tying two production fabrics. i.e. Production servers in one DC to production storage in another DC. In this case, the transit will protect your non-IVR devices from seeing switch and end-device disappearances if the transport is lost or bounces frequently.
Unfortunately, IVR design is difficult to generalize. Simple designs and best practices do not necessarily scale. It's always best to throughly review IVR designs with folks that have been through it before."
I took particular note of the words in bold, which also speaks to my reasoning for preferring use of VSANs over zoning alone and/or the absolute simplest design available. With all due respect, I view use of VSANs as offering better scalability, availability, and security, and I am trying to prepare in advance for an environment I know is going to scale quickly. The above scenario was posited for simplicity; it is not the actual config, number of switches, or complete environment.
With this post, I am specifically interested in soliciting expert advice on use of transit VSANs, with the assumption that the example scenario is required. I am not necessarily after value judgments of Cisco technology, even though I do respect and appreciate opinions along those lines.
by: andyalderPosted on 2009-09-18 at 02:19:38ID: 25364068
>The file server is in VSAN 2 and the tape library is in VSAN 10.
Why are they in different VSANs? VSANs are very rarely necessary, we got away without them until Cisco entered the SAN business a few years ago and no doubt we'll get away without them in the future.