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ERS, CI and DB Cluster riddle

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Hi Experts,

Can ERS be installed outside /usr/sap?

I am having a typical CI DB cluster scenario (Veritas).

One Virtual Host for Central Instance with the /usr/sap and /sapmnt attached to it.

One Virtual DB host with /Oracle attached to it.

The above two is arrange on a two node cluster using two physical machine as well as one storage box. So that at any condition of any physical node down I always get the above two virtual hosts (cluster nodes) with the required directory attached in it. At normal condition Virtual Host for CI is on physical host P1 and Virtual Host DB is on physical host P2

I do not have any third machine, and in this context I would like to establish ERS. I have no issue to put ERS20 on Virtual Host CI, as the /usr/sap/<SID>/ERS/ERS20 can be there without any issue. But the ERS21 if I need to put on the Virtual Node of DB, then the  directory /usr/sap/<SID>/ERS/ERS21 can be overwritten if the P1 goes down and Virtual CI shifts to N2. This is Vice Versa if P2 goes down and Virtual DB shifts to N1.

In this situation, I am looking for an option where I can control the installation of ERS22 and change the installation directory something other than /usr/sap or /sapmnt or /oracle. Is it possible? Then how?

Regards,

Soumen.

Accepted Solutions (0)

Answers (2)

Answers (2)

Former Member
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you need a HA-NFS cluster solution for managing /usr/sap and /sapmnt filesystems

the ha-nfs you may try configuring it in the same cluster or you can build them in separate cluster

Regards,

Chandru

former_member188883
Active Contributor
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Hi Soumen,

ERS has to be a local installation and it will use /usr/sap folder for installation.

So instead of putting entire /usr/sap into cluster configuration add /usr/sap/SID in cluster configuration.

ERS will be installed locally under /usr/sap and during failover it won't be moving from one node to another.

Hope this helps.

Regards.

Deepak Kori

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Hi Deepak,

Feel this is not solved.

Because even if I install ERS21 physically on P2 (installation directory goes something like /usr/sap/<SID>/ERS...) and P1 gets down for any reason and Virtual CI moves over to P2, then also it will not be visible. Isn't it?


former_member188883
Active Contributor
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Hi Soumen,

Correct. Then my suggestion is put only following file systems into cluster or make it available on both the nodes

1) /usr/sap/trans

2) /sapmnt/SID

3) DB related file systems

4) /usr/sap/SID/ASCS

Rest other components and file systems is local and out of cluster.

Hope this helps.

Regards,

Deepak Kori

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Hi Deepak,

Yes, I gave it a thought, but then how /usr/sap will be accessed from Virtual Node CI?

Every time for a switch, then we need an effort to network mount the /usr/sap file system....Will not the entire logic of cluster goes away?

Is there not any mechanism to change the installation directory?

former_member188883
Active Contributor
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Hi Soumen,

What is that you want to access from /usr/sap ?

As per SAP guidelines you can have following setup done for HA

1) Node 1: DB on virtual host + ERS on local hosts

2) Node 2: ASCS on virtual host + CI on local hosts

You need to have following file systems available on both the nodes

1) /usr/sap/trans

2) /sapmnt/SID

Local installations will have local folders which will not move to another node.

I have done this setup many a times and it works without fail.

I am not sure how you have built your HA solution ?

Request you to discuss the solution proposed with your H/W vendor responsible for HA and test this out.

Regards,

Deepak Kori

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Hi Deepak,

The point is, what will happen for the for other directories of /usr/sap,

e.g. /usr/sap/ccms, /usr/sap/DXX and /usr/sap/tmp?

I mean when Virtual Host moved to P2 because P1 is not available, will host and diagnostic agent remain stopped? because in that case their directories are all in physically lying over P1 and remain unavailable as P1 is down....

A soft/network link will not work and in that case, these directories need to be kept as a copy to both the physical node.

Regards,

Soumen.

former_member188883
Active Contributor
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Hi Soumen,

CCMS & Host agents needs to be installed on each and every host. For HA since there are 2 nodes you need to have them installed on each node.

Keep the path of installation same on both the nodes.

Regards,

Deepak Kori