HPE EVA Storage

Alternate ISL with Continuous Access

Regular Advisor

Alternate ISL with Continuous Access

I have two storage P6500 in sites A and B with two fabrics replicating with Continuous Access. This is the topology:

Fabric 1:

(LE E-Port ) <=====================> (LE E-Port)
Switch 1A                              Switch 1B

Distance ISL = 8 Km

Fabric 2:

(LE E-Port ) <=====================> (LE E-Port)
Switch 2A                              Switch 2B

Distance ISL = 8 Km

For high availability, I want to add another ISL in fabric 1, on this manner:

(??? E-Port) <=====================> (??? E-Port)
Switch 1A-2                    Switch 1B-2

The desired distance for this ISL is 30 km.

My question is:

1. How I configure the port for supporting the 30 km ? Is there a "load balance" in the switch with two ISL on different distances ?
2. Is there a special consideration with the configuration of switch / port if I'm using Continuous Access ?

Please, provide me any clues according your experience.

Thanks in advance.



P.S. This thread ahs been moved from General to Storage Area Networks (SAN) (Enterprise). - Hp Forum moderator

Johan Guldmyr
Honored Contributor

Re: Alternate ISL with Continuous Access

1.) You set different "portcfglongdistance" settings on the switch-ports. If you're over 10km you will likely need a special license for those modes. More details about which modes to choose from are in the Fabric OS Administrator's Guide. Generally, if you have a longer link you'll need more buffers on the port to keep it at high speed.

To load balance between ISLs you would use trunking, there may however be limitations where this won't work if the difference in length/delay is too much. If you have trunking license and the switch allows the two links to be joined in a trunk, it will join them automatically. Restrictions would be in the Fabric OS Admin Guide too.

2.) In CA you get to choose between different replication protocols. That's if you use port-based/exchange-based routing. Another thing to keep in mind is to dedicate links for CA. HP has a "Continuous Access Implementation Guide" and a SAN Design Reference Guide, these may have more information for you too.
Occasional Visitor

Re: Alternate ISL with Continuous Access



What type of SAN switches are you using? In the case of Brocades, you have to create an ISL trunk using the addiitonal link. Once the trunk is formed, a cost will be assigned to each member in the trunk. The routing protocol routes the packet using the least cost link. Check the licensing requirements for Brocades.


 For CISCOs, you have to create a port channel using both ISLs.


You can route the CA traffic through one channel only if you use VSANs/VFabrics and limit that VSAN to the ISL you want to use.