Install a non-clustered SAP instance on a Windows cluster

[john_studdert]

Any SAP installation uses a sapmnt share of course. On a Windows cluster, this needs to be set up as a clustered fileshare with a virtual hostname/IP. Has anyone managed to install a non-clustered SAP system on a server that is a cluster node that co-exists with a clustered SAP installation? This in effect would mean you have two sapmnt shares on the same Windows server - one a local fileshare, one a clustered fileshare.

So let's say we have D11 installed on a 2-node Windows cluster. It is properly installed with the ASCS and ERS instances being installed as part of the SAP cluster service group and on a clustered disk, with sapmnt created on that as a clustered file share.

We also have D12, which is installed on a local disk on node A. That local disk has a local fileshare called sapmnt that D12 uses.

Ignore for a second the questions about why you would want to do this 🙂

I've actually got this much working, but my issue is when I fail over from node A to node B or vice-versa. When the clustered SAP system starts back up, sapcpe runs to sync binaries. sapcpe's start profile specifies the source kernel directory. What happens quite a lot here is that it picks the wrong sapmnt share and either copies the wrong kernel or can't find the file path at all and the startup fails.

Just wondering if anyone has looked at this type of set up before. The primary reason for this setup is due to a local web dispatcher being installed alongside the clustered SAP installation.

[isaias_freitas · Accepted solution]

Hello John,

The failover issue occurs because of the conflicting sapmnt shares.

This is discussed at the item 5 from the SAP note 112266.

In order to make this work, I believe that you would need to use a virtual hostname for the non-clustered system as well.

There is a section about using multiple SAP systems at the same server, at the SAP Installation Guides. I believe that could help in this case.

Regards,

Isaías

[john_studdert · Accepted solution]

Thanks Isaias, appreciate that. Yes that is exactly the issue we have but thank you for the SAP note which explicitly states it's not supported.

We do indeed use virtual hostnames for the non-clustered systems as well but I suspect the problem is that despite this, when they are registered on the same NIC Windows does not reliably resolve them.

There is a technet article that reflects this. Based on that I'm going to mark this closed and the answer is that this is not possible or supported, even if you use virtual hostnames and de-select registering with DNS on the NIC (and then manually create static DNS records instead), as we are using these on the same NIC.

[isaias_freitas · Accepted solution]

You're welcome!

[Sriram2009]

Hi John.

In which Windows Server OS ? If it is Windows 2008 and above you can install the one more instance on either one of the cluster nodes based on your hardware resources and it should conflict existing cluster instance number.

BR

SS

[john_studdert]

Thanks for the input S! Yes that's right (in fact you could install more than one instance on the cluster on Win2003 as well but it was a lot more complicated and not recommended).

However, that's not my scenario. What you're describing is installing a 2nd SAP instance into the cluster - so as long as it's got a separate cluster service group you don't have an issue (cluster file shares can have the same name as long as they're in separate groups).

My scenario is installing a local (non-clustered/non-cluster aware) SAP instance using a local "sapmnt" fileshare. In this scenario, no matter how we set up the start + instance profiles for all the SAP instances, we cannot get them to reliably use the correct sapmnt share for that instance.

Ultimately we've had to install the local instances on a separate server outside of the cluster. Since that appears to also be the strategic direction that SAP are taking from an architectural point of view from Windows 2012 onwards (e.g. you have to install local SAP instances outside of the cluster if you want to use the new continuous availability feature), and since it simplifies the configuration dramatically, we think this is just a better solution anyway.

However, I'm still curious as to whether it's actually possible to get the scenario I describe reliably working even in the event of cluster failovers.

[Sriram2009]

Hi John.

  I understood what is your requirement, without Cluster you can install the second SAP instance (Without cluster standalone SAP instance)in either one of the cluster nodes based on your hardware resources and it should not conflict any port on existing cluster system while installation of standalone instance.

BR

SS

[john_studdert]

Thanks S. The conflict isn't with port numbers/instance numbers of systems - the problem is the requirement for a local sapmnt fileshare for the non-clustered SAP installation.

Having two sapmnt shares means that when starting up, the SAP system is using the wrong sapmnt to use as a file path to get the kernel files for sapcpe. It does this no matter how much we play with the start + instance profiles to hard-code the file paths.

[Sriram2009]

Hi

In Windows 2008 and above  SAPMNT share folder was created in the virtual name of the SAP cluster group(Not on physical either of the nodes).

You are going to install the second SAP Standalone system on either one of the physical nodes(Not on Cluster ).in that case share going to create on physical node(Not on SAP cluster group)

For example-

1. Existing Two Nodes Failover Cluster system.

Two Node windows failover cluster systems Physical Node A & Physical Node B

Share folder for Cluster environments - in Virtual Name - C (SAP Cluster group)

For cluster system all the share created on Virtual name C (Not on Nodes A or B)

2.  Either one of the Nodes Standalone SAP instance

You are going to install the second SAP Standalone instance on either one of the Nodes(A or B). all the SAPMNT share start+ instance profiles are going to create either one of the Nodes(A or B), In this system your are not used the existing cluster instance numbers

Regards

SS

[john_studdert]

Yes that pretty much describes what we've installed and what I've been trying to describe in this thread. However, it doesn't work - at least not reliably.

When the SAP cluster service group is on the same node as the local installation, there are then two sapmnt shares on the same server: one a local fileshare, one a clustered fileshare. When that happens, Windows resolves the UNC path to the fileshare unreliably (i.e. we can't force it to point to the clustered fileshare or the local fileshare reliably).