FAS2552 HA pair direct attach with C240

[KevinTang]

Hi everyone

    I am trying to make a FAS2552 HA pair to work with a Cisco C240 server by using direct attach connection, I have tried FCoE and iSCSI but cannot get it to work, I have read from Netapp documentation that FCoE is not supported in direct attach but iSCSI should be support, anyone have experience on iSCSI direct attach of HA pair before?

Kevin

[aborzenkov]

"Cannot get it to work" does not give much starting point. Explain what you have done, what you expected and what are results.

And start with telling which version and mode of Data ONTAP you have.

[chott]

Hi Kevin,

my name is Chriz Ott, I'm working with NetApp as a Principal Architect.

Thank you very much for bringing this topic up, as I have seen this very often.

Unfortunately we do not support SAN configurations (FCP, iSCSI or FCoE) directly attached to FAS storage systems, as we are providing high availablity by using ALUA and MPIO. From the Scalable SAN FAQ:

"Is a direct-attach configuration possible?
Answer: No. The failover capability of clustered Data ONTAP requires an active path to a node’s HA partner. Furthermore, in the case of Fibre Channel configurations, direct connections do not support the N_Port ID virtualization (NPIV) facility."

In order to help you setup your environemnt I can recommend i.e. the iSCSI for Windows Express guide:

https://library.netapp.com/ecm/ecm_download_file/ECMP1547466

Other Express Guides are available under:

http://mysupport.netapp.com/documentation/docweb/index.html?productID=61885&language=en-US

Also if you would like to get more detailied information please refer to the SAN Administration Guide:

https://library.netapp.com/ecm/ecm_download_file/ECMP1636035

Most important make sure your configuration has been tested and is supported. You can find this information using the Interoperability Matrix:

http://mysupport.netapp.com/NOW/products/interoperability/

Simply Select "SAN" in the top-center as your storage solution, where it says "change".

And then select your infrastructure components from the left pane. (Server, OS, ONTAP OS etc)

I hope this helps, please don't hesitate to contact me in case you have additional questions.

Cheers chriz

P.S. I you feel this answer is helpful, please mark as KUDO or "correct answer", to make it easier for others to find.

[aborzenkov]

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Unfortunately we do not support SAN configurations (FCP, iSCSI or FCoE) directly attached to FAS storage systems, as we are providing high availablity by using ALUA and MPIO. 

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This does not explain why direct host connection with iSCSI is impossible. Host having 2 ethernet adapters, each to different controller, and using MPIO over these two adapters. What does not work in this configuration?

FCoE is not possible because it requires management instance which is normally implemented by switches and FC may have problems with NPIV as you mentioned. But I miss the reason why iSCSI should not work.

[chott]

Hi Aborzenkov,

I never stated it wouldn't work, I just stated it was not supported, which is what we should be interested in 🙂

cheers chriz

[KevinTang]

Hi Chris

     I am a bit confused, so iSCSI direct attach is not supported but it might work? Can you explain more? Thanks!

Regards

Kevin

[chott]

Hi Kevin,

if you follow the steps in the Express Guides you will probably get it to work, but even a vol move may break your connection, so it is not recommended and not supported!

cheers chriz

[KevinTang]

Hi Chris

    So you mean iSCSI with HA is not possible, so a vol move between the node will cause the connection to break? Is this only apply to cluster mode? If I use 7 mode is it possible to use iSCSI without problem?

Best Regards

Kevin

[aborzenkov]

No, in 7-Mode it is near to impossible to get right. The problem is, 7-Mode iSCSI does not use ALUA so it relies on simple IP failover. If you have direct controller connection and controller goes down, IP is moved to partner, but host is still connected to the same controller that is not available anymore. So it cannot access target IP. 

But C-Mode is using ALUA where LIFs themselves do not migrate. So host has two (or more) independent paths to two different controllers. I honestly fail to understand how switch connection differs from direct connection here.

[jbhakta]

How about NFS? Does it supported, If ESX server is directly attached on FAS2552?

[aborzenkov]

It has the same problem - IP address fails over to another port, but host has connection to old port that does not work anymore.

[shatfield]

For what its worth, direct-connect ISCSI is supported but only in a non-ha configuration.  Why would be an interesting discussion, but its called out explicitly in the documentation.

[RickStratton]

I would be interested to know the technical reasons why direct-attach iSCSI in an HA configuration is not supported, even though there are indications that it will/should work.

If I have the following config:

• NetApp_Controller-A
  • e0c ---> Host_P1
  • e0d ---> Host_P2
• NetApp_Controller-B
  • e0c ---> Host_P3
  • e0d ---> Host_P4

In the above configuration, the host MPIO should see [4] paths to a LUN.

In the event of a controller failure, where the SVM would only have LIFs on the surviving controller, the host MPIO would detect the failure of [2] paths, but have [2] remaining paths (since the NetApp iSCSI LIF's can only be configured as "Failover Policy: disabled", they can't migrate from the failing controller to the surviving controller).

Previous posts indicate that "it will work, but is not a supported config"... so, I am interested in the technical issues that led NetApp to not support the configuration, even though it will/should work.