Service Guard with RAC

[Syed Muqtader Ali]

Dear Experts ,

Since long time iam getting confused on one issue and the issue is

basically their is oracle 10gRAC installed on 2 hp nodes and its connected to san for shared memory disk here they installed the service guard too
Please my question is any one can give me clear picture why they need to installed service guard on over setup

awaiting replie

[Court Campbell]

To keep it simple -- you need to have serviceguard installed in order to run rac on hp-ux. unfortunately it is not like a rac install on Linux where you don't need a third party clustering software.

[Steven E. Protter]

Shalom,

With RAC version 9 on HP-UX serviceguard was a requirement prior to installation.

For 10gRAC, it is not a requirement but it may be depending on how you intend to use 10gRAC.

To maintain shared storage under certain circumstances you may still need serviceguard.

Whether or nor you need it is dependent on how you intend to use RAC and what options are needed. I just had a conversation on this with a DBA 30 seconds ago and he assures me that Serviceguard may not be required for 10gRAC, which has its own built in clustering software.

SEP

[Syed Muqtader Ali]

Thanks for sharing knowledge friends..

In 10grac , basically it used Clusterware software (OCR+ voting disk) for oracle clustering.. so then what is the requirment of service guard

Court Campbell, you mean to say that Service guard is used to do operating system kind of Clustering

Sep, To maintain shared storage under certain circumstances you may still need serviceguard.

please can you describe the circumstances under shared memory storage for SAN

Cheers
Syed

[Steven E. Protter]

Shalom again,

One thing I saw that makes no sense was that one shop running oracle RAC wrote all logs to an NFS share that was controlled by the "active" node.

This was to permit the second node to write to the shame NFS share.

Few problems: NFS log writes going through the network, which was 100 BaseT are substantially slower than writing directly to shared storage, which was accessible to both RAC nodes.

But the site refused to drop NFS, so serviceguard had to be installed to make sure the NFS share stayed with the active node.

I do not believe you NEED serviceguard with 10G unless your configuration has requirements to manage some resource that the Oracle clusterware software can not manage. Such as a NFS share.

SEP

[Duncan Edmonstone]

Why would you use the Serviceguard clusterware if implementing RAC on HP-UX?

There are a few reasons I can think of:

i) Network protection - Serviceguard provides protection from network failure, CRS doesn't.

ii) Interconnect monitoring - Serviceguard can monitor and take action on the cache fusion interconnect more effecitively than CRS.

iii) Kernel integration - CRS is an all user space process, whereas Serviceguard is able to take advantage of the kernel safety timer - this provides much better hung node detection on HP-UX. Note on Linux Oracle can and do have a kernel module that provides a similar function.

iv) Cluster Filesystem - some people can't or don't want to use raw disks or ASM - With Serviceguard you also have the option of using a cluster filesystem.

v) Integration with HP's other products - Serviceguard is welll integrated with HP's other products like the VSE suite and disaster tolerance solutions like ContinentalClusters or Metrocluster.

vi) Maturity - OK this one is pretty subjective, but I happen to think that Serviceguard is simply more reliable and simpler than CRS - others will no doubt disagree.

vii) Other applications - More often than not an application is more than just a database - how do you provide HA for those other components with CRS? This one's also slightly subjective, as CRS does in theory support other apps apart from RAC, but in reality I've hardly ever seen anyone use it for anything apart from RAC. Serviceguard has a rich heritage of proof points with many, many applications.

No doubt there are other reasons, but theres a few to consider.

HTH

Duncan

[Court Campbell]

SEP,

I have not seen a 10gRAC install on HP-UX that did not require serviceguard and the serviceguard extnesions for rac. I think the note at the end of this page says it all:

http://h20247.www2.hp.com/enterprise/cache/314513-0-0-0-121.html

*Note: Serviceguard and SGeRAC are required components for Oracle9i RAC and 10g RAC on HP-UX 11i servers. Serviceguard is included with the HP-UX 11i Mission Critical Operating Environment, but SGeRAC is ordered separately.

Maybe I am missing something.

[Syed Muqtader Ali]

Syed again .......


My Friends as per my understanding regarding your our conversation is the Major use of Serice guard is to manage NFS and i think this is a correct cuz here in our systems we are using NFS OCR and RAW for database files.

Thanks all
syed

[Yogeeraj_1]

hi Syed,

also have a look at the metalink note with subject: Raw Devices and Cluster Filesystems With Real Application Clusters
(183408.1)


This document gives an RAC overview and a comparison of raw devices, ASM
and Cluster File Systems across several operating systems.


hope this helps!
kind regards
yogeeraj

[Duncan Edmonstone]

Court,

That note is, unfortunately not quite accurate. Whilst 9iRAC *had* to use SGeRAC, for 10gRAC, you can if you wish just use Oracle's own clusterware.

HTH

Duncan