About multipathing, MPIO, and EVA

[Luis_135]

I have an EVA8100 SAN that is working just fine.

I would like to know how is one path chosen among all of the paths available.

In my case, i have eight paths to each host. I didn't configure anything about how to choose the active path in the host, the only thing i did was to install MPIO, and i guess that this is the software that takes the decision of which path to use. Is this right? How does it takes the decision? Based on what parameters? Link, speed, available bandwidth?

Another question. Ig i have a dual port 4 Gb HBA in one host, is it possible that both ports are used at the same time? Maybe the host can see one LUN through one port and another LUN through the other port. Is this right?

Thanks

[Ivan Ferreira]

>>> The only thing i did was to install MPIO

¿Which MPIO software? There are options, and some allows you to set the preferred path, other no.

>>> Ig i have a dual port 4 Gb HBA in one host, is it possible that both ports are used at the same time?

Yes, it's possible.

>>> Maybe the host can see one LUN through one port and another LUN through the other port. Is this right?


Yes, just configure different hosts and ports in the EVA hosts folder for each HBA. Present the VDISK to these hosts.

It seems that you have one HBA with two ports, in this case, you have a single point of failure.

[Emil Velez]

I hope you have the qlogic cards and not the emulex. The emulex is only supported for single path solutions on linux.

THe qlogic driver handles the multipathing in linux and the software does the active/active (since it is a EVA 8100) path selection and failover.

[Brem Belguebli]

To Emil Velez,

>I hope you have the qlogic cards and not the emulex. The emulex is only supported for single path solutions on linux.

No, it is not true. Linux, since kernel 2.6.x comes with device-mapper multipath (DM-MP) and handles multipathing in a round-robin fashion (multibus) with Emulex and Qlogic HBA's.

>THe qlogic driver handles the multipathing in linux and the software does the active/active (since it is a EVA 8100) path selection and failover.

In fact it's the DM-MP that handles the multipathing not the HBA driver, that's why it works with emulex and qlogic, and should work with any kind of HBA.

To Luis,

What MPIO software are you using ? Native Linux DM-MP driver ?
By default, with EVA8100 and DM-MP, you should see 2 priority groups of 4 pathes each per LUN, with only 1 group active (4 ports) in round-robin.
You can reconfigure it to allow you to load balance accross the 8 ports.

It is always recommended to present the Luns to all your ports preventing a cable failure for instance.

Brem

[Luis_135]

Thank you all for your answers.

Actually, my question is more about Solaris. I didn't mention operating system of the hosts involved, but i am planning to connect Solaris 9 and 10 with integrated MPxIO.

Thanks again!

[Luis_135]

I forgot!

HBAs are Qlogic from SUN.

Thanks!

[Brem Belguebli]

Hola Luis,

This forum is more Linux Serviceguard clustering oriented.

Try reading the doc at the link below, it'll help you configuring your Luns.
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00854937/c00854937.pdf

Regards