PDA

View Full Version : Multipath for HP MSA iSCSI Array



LarryResch
21-Jul-2015, 17:45
I have an HP MSA with dual controllers (4 Ethernet ports per controller) connected to a network switch. My SLES 11 SP3 server has a single 10G connection to the same switch. I want to maximize the throughput to the MSA and it looks like I will use multipathing. I have it set up and multipah -ll shows both controllers, but my question deals with using all 8 ports for the connection.

Do I need to do anything if I want to use all of the Ethernet connections between the switch and the MSA? Under YAST, iSCSI Initiator, I have discovered all 8 IP addresses for the MSA controllers and have logged on to each. Is there anything else I need to do or not do?

TIA
-L

jmozdzen
21-Jul-2015, 18:36
Hi Larry,

> Do I need to do anything if I want to use all of the Ethernet connections between the switch and the MSA?

this mostly depends on the setup of the MSA box - does it aggregate the four links per controller (and if so - how?), or are all links individually (and deterministically) reachable via independent IP addresses? IOW, do you currently have two paths defined? Or does the MSA offer 8 individual addresses, and map traffic to a dedicated link per address (I doubt that)?

As you have a single end point on your iSCSI initiator (single 10G Ethernet adapter), you wouldn't benefit from any link aggregation that is balancing sessions across the four links (per controller) IP- or MAC-based - you'd just use two of eight links concurrently.

Regards,
Jens

LarryResch
24-Jul-2015, 14:09
Hi Larry,

> Do I need to do anything if I want to use all of the Ethernet connections between the switch and the MSA?

this mostly depends on the setup of the MSA box - does it aggregate the four links per controller (and if so - how?), or are all links individually (and deterministically) reachable via independent IP addresses? IOW, do you currently have two paths defined? Or does the MSA offer 8 individual addresses, and map traffic to a dedicated link per address (I doubt that)?

As you have a single end point on your iSCSI initiator (single 10G Ethernet adapter), you wouldn't benefit from any link aggregation that is balancing sessions across the four links (per controller) IP- or MAC-based - you'd just use two of eight links concurrently.

Regards,
Jens

The MSA has 8 ports with an individual IP address for each port. Yes, I now have a single 10G connection from the server to the SAN switch. The server I assume is using the single path to the switch, but I am wondering that since the iSCSI Initiator is connecting to all 8 IP addresses for the MSA, that it is using multipathing to connect to those IP addresses.

I just want to make sure that I am not doing something wrong or need to do something to get this working correctly.

-L

jmozdzen
27-Jul-2015, 17:01
Hi Larry,

> The MSA has 8 ports with an individual IP address for each port. Yes, I now have a single 10G connection from the server to the SAN switch. The server I assume is using the single path to the switch, but I am wondering that since the iSCSI Initiator is connecting to all 8 IP addresses for the MSA, that it is using multipathing to connect to those IP addresses.

I cannot help with any multipath configuration aspects and will have to leave that to other users active here, but a small note on the subject of IP networking: If the 8 IP addresses of the MSA are within a single subnet, you might want to check that outgoing traffic (from the MSA to the initiator) isn't bundled on a single link (because of IP stack routing limitations). If the MSA has implemented sending out responses on the link it received the request, all is well.

Regards,
Jens