Fabric Segmentation

[Manish K]

What are the effects of Fabric segmentation?

[Johan Guldmyr]

Is this what you're talking about?

http://h30499.www3.hp.com/t5/Storage-Area-Networks-SAN/What-s-a-segmented-Fabric/m-p/4273565#M33223

Why most setups intentionally have two fabrics?

Or, while trying to merge a switch, but for some reason it can't and it's then 'segmented'.

[Manish K]

that thread doesn't give any info about its effects.

The situation i am asking is " There is Running Fabric with multiple switch. under what condition a running fabric can get segmented and what could be its side-effects?."

[Johan Guldmyr]

Ah okay.

If a switch in a multi-switch fabric gets segmented (that means isolated). Then devices in that switch can only communicate with other devices in that switch.

Causes for this could be ISL problems (changed switch settings, portconfigs).

[Manish K]

okai... can it have any kind of effect on the host?

[Johan Guldmyr]

Yes of course.

Let's say you have a fabric with switches A and B.

On switch A you have a bunch of servers.
On switch B you have connected some disk arrays and tape libraries.

Switch A and B are connected with an ISL.

If for some reason the two switches get segmented (which means they are not in a fabric) then the hosts cannot see the storage device.

This is why it's a good idea to do upgrades/config changes on one fabric at a time, in case it doesn't go well.