Using 2 dual port HBAs how many path can serve data at the same time.

Question

Hi,

Today I suggested my windows administrator to use 2 dual port HBAs on his server. He asked me what is the benefit and I explained he can map the ports each port on those hba to 2 SP port. This way he will get 8 IO streams and all of them can server data at the same time. Is that possible??? If not, then how many paths can actively server IOs at the same time using ALUA and 2 dual port HBAs.?

Regards,

Nishant Kohli

818 584 5956

dynamox · Answer

You should not exceed more than 4 active paths

Nishant_Kohli · Answer

Dynamox - Thank you for the reponse.

However, do you mean that the data will be served simultaenously by atleast the 4 paths. Look at the below scenerio.

Win-host HBA1 HBA1 Port1- SP A1 Switch - 1

HBA1 Port1-SP B1 Swich - 1

HBA1Port2- SP A2 Switch - 2

HBA1Port2- SP B2 Switch - 2

HBA2 HBA2Port1- SP A3 Switch - 1

HBA2Port1- SP B3 Switch - 1

HBA2Port2- SP A4 Switch - 2

HBA2Port2- SP B4 Switch - 2

In the above configuration we have Windows host "Win-host" with 2 dual port HBAs HBA1 and HBA2. You can see how zoning has been configured for this host on 2 fabric switches Switch1 and Switch 2.

Please suggest how many paths should be actively surving IO throguh this setup. I understand.. we have 4 paths to SPA and 4 to SPB. And suppose the LUN is on SP A. And we have powerpath configured on this host with ALUA option.

Will the host be surving IO only by 1 optimal path. Or can the data simultaneously flow through 4 paths?

dynamox · Answer

what you have is perfect, if LUN is owned by SPA and you are using licensed PowerPath then you have 4 active paths, every port is being utilized to send data simultaneously to SPA.

Nishant_Kohli · Answer

Dynamox - Are you sure that host should serve/send IOs via all 4 paths to SPA????

Because what I read from the documents related to powerpath: It can only send IO via single optimum path ideally. Only when there is heavy load, powerpath decides to choose a different path of data transfer ??????

As per what you are saying, do you think putting a 2 dual port HBA would give a host better speed over using 2 single port HBAs in below configuration?

Win-host HBA1 HBA1Port1- SP A1 Switch - 1

HBA1Port1- SP B1 Swich - 1

HBA2 HBA2Port1- SP A3 Switch - 2

HBA2Port1- SP B3 Switch - 2

Regards

Nishant Kohli

Storage - Guitar Center, ITO | Desk: (818) 735-8800 ext 2835

Mobile – 818 584 5956

E: Nishant.Kohli@Guitarcenter.com

dynamox · Answer

yes, licensed PowerPath will use all paths to an SP that owns the LUN. It depends how much I/O you are pushing, having more paths will create more queues in the OS and potentially give you better throughput.

there are some example in this document

http://www.emc.com/collateral/software/white-papers/h8180-powerpath-load-balancing-failover-wp.pdf

dynamox · Answer

make sure to select correct policy 'clariion' or 'vnx'

Nishant_Kohli · Answer

Ok.

How about the second scenario where you see 2 single port HBAs.

Do you think, in a normal scenario the host serves IOs through both the HBAs at the same time, using ports A1 and A3 on SPA?

Or do you think, only if HBA1 fails the path through HBA 2 – SPA A3 would become active?

Regards

Nishant Kohli

Storage - Guitar Center, ITO | Desk: (818) 735-8800 ext 2835

Mobile – 818 584 5956

E: Nishant.Kohli@Guitarcenter.com

dynamox · Answer

both HBAs will be sending data to SPA at the same time

Nishant_Kohli · Answer

Thanks Dynamox. Is there any special policy to be chosen for this operation. Or is this the ideal configuration for I/Os.

Because what we are trying to achieve is, use 2 dual port HBAs and get 4 paths serving IO to 1 SP at the same time.

Regards

Nishant Kohli

Storage - Guitar Center, ITO | Desk: (818) 735-8800 ext 2835

Mobile – 818 584 5956

E: Nishant.Kohli@Guitarcenter.com

VNX

Using 2 dual port HBAs how many path can serve data at the same time.

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