FCP Array Interface (ext_bus) Instance number

[manamirhastam]

I'm using a combination of rx2620 and EVA4000.
Before adding the new enclosure to EVA , the instance number of FCP Array Interface (ext_bus) was 5 , so I had the device files with c5txdx structure and now after adding enclosure to EVA a new number has been assigned as the instance number.
Actually I know how to change the instance number , but I just want to know what's the reason of this change ?
Because I exactly performed same steps on test environment and after adding enclosure there was no change.
But in the Production environment now I have a different instance number for ext_bus.
Acctually I want to use previous device files but the new instance number is creating new device files for EVA vdisks.
Any idea ?

[Sandman!]

Are these attached to the host directly or thru a SAN?

[manamirhastam]

It's EVA4000 with two HSV200 controllers connected to SAN switch.

[Sandman!]

Were there any changes made to the environment either on the host, the SAN side or the storage array. In my experience HP-UX will not change the c# unless there has been a change in the environment somewhere.

[manamirhastam]

Hi Sandman
These is no change !
That's why I'm confused .
I just added one more enclosure.
As I told in another environment we don't have any problem. But everything is same .

[Torsten.]

HI,

"Because I exactly performed same steps on test environment and after adding enclosure there was no change."

What steps?

If the bus is "full", the system will create a new cx(tydz) instance and will continue to count the LUNs (vdisks) presented from the EVA.

[manamirhastam]

Hi Torsten,
During installation the new enclosure there was no change on server side .
Same HBA and same structure.
Actually I performed these steps on two environments.
the first one has two rx4640 hp servers and two HSV200 controllers and also two enclosures.
The only difference on second environment is two rx2620 servers , but the EVA is same.
Before adding the new enclosure on both environments , I had similar FCP instance number on both rx4640 and also both rx2620.
After the new enclosure installation there was no change on rx4640 servers , but on rx2620 servers the FCP instance number had been changed.