Cascaded hubs- will it let us lookup for the disks, even if the controller fails?

[Anu Mathew]

Hi all,

The attachment is a schematic representation of the proposed setup. We intend to connect two servers, both connected to the same FC60, with 6 sc10 Enclosures, running on Full Bus Mode. Each enclosure houses about 6 73 GB disk drives. Both the servers would run different applications and Luns are created for them with mirroring and RAID 5.

Server 1 connects to the HUB1, which is directly connected to the Controller A. We are also using disks on Controller B.

The question in hand is, if Fibre Cable 1 fails, will we be able to lookup for the disks pertaining to that, via HUB2, since both the HUBs are cascaded?

Thanks in advance for your time and valuable suggestions,

Anu Mathew

[Stefan Saliba · Accepted solution]

The cascaded hub is not needed.
All you need to do is make sure that you
configure and alternate link on both servers
in lvm. i.e. one that passes from hub one and the other that passes from hub 2. Removing the cascaded hub will create two loops and then each server will have two paths it can take one from each loop to reach the LUN on the fc60

thus removing fibre cable 1 will still leave another route from hub2 IF AND ONLY IF you configure the alternate path in LVM

[Pedro Sousa]

Stefan is absolutely correct.
The only thing you need to do is:
'ioscan -fnC' disk to find out wich are the alternate HW paths that point to the disks in use.
then perform a vgextend to those disks.

For this you should have a configuration like the one in my attatchment (it's an Winword doc :))

good luck.

[Pedro Sousa]

Sorry, but I only saw your draw now!!
So, again as Stefan said, you don't need those hubs to be in cascade mode!

[Anu Mathew]

Hi Gentlemen,

Thanks a lot for replying. Your replies were very useful and I appreciate your efforts.

Thanks once again.

Anu Mathew