General questions on Serviceguard (planning an installation, and teething problems).

[Iain Soedring]

Hi,

I'm looking at using Serviceguard to create a simple High-Availability cluster of Apache httpd servers.

Looking at the documentation on this product, there's a lot of talk about shared disk volumes, SAN etc.

What I want is just three httpd servers configured so that if the 'master' server fails, one of the others will take over, using a reallocatable IP address. This is all I want, no shared volumes, no quorum server, nothing else.

Looking at the hp documentation it appears Serviceguard may be too 'heavyweight' for my needs.


My questions are:
1. Is my simple web server simple possible with Serviceguard, or do I need to create shared disk volumes?

2. I have version 11.17, are there any fixpaks I need for this? I keep getting 'Node refusing Serviceguard communication', despite following all instructions on working around not having identd running, setting up cmlnodelist etc.

[Ivan Krastev]

You can create Serviceguard cluster with packages without shared disk, but you will need a quorum server for cluster locks.

No problem to create the package without shared storage - in package control files just add httpd stop and start scripts.
When package fail from one node to another it silmply will do the following:
node1: stop httpd
node1: remove shared IP
node2: apply shared IP config
node2: run httpd


regards,
ivan

[Iain Soedring]

Thanks Ivan, but will I still need a quorum server if I have three nodes?

[Ivan Krastev · Accepted solution]

Quorum server is used as a cluster lock no matter how many nodes you have.

It is recomended for more than 3 nodes cluster and in your case (you don't have a cluster lock disk) it is mandatory.

See more info about quorum here - http://docs.hp.com/en/B3936-90078/ch01s06.html

regards,
ivan

[Thomas J. Harrold]

If you have an extra Linux server (or an older Intel server that could host Linux), you can run quorum services on that node.

Alternatively, you can create a 2 node cluster and have the 3rd node run your quorum service.

QS is supported on RedHat, Suse, and HP-UX. It would be nice if HP would support it on Windows as well. On second though, maybe not... :)

-tjh

[Colin Topliss]

I wouldn't bother with ServiceGuard - HP are dropping it for Linux.

Have a look at RSF-1, LifeKeeper, or even the cluster technologies for your distribution.

RSF-1 certainly doesn't use lock-luns or a quorum server.

Discontinuation notice can be found here:

http://h18026.www1.hp.com/solutions/enterprise/highavailability/linux/serviceguard/discontinuance.html

[Thomas J. Harrold]

Any clustering product that doesn't use lock luns or some sort of cluster arbitration should be considered risky at best.

[Colin Topliss]

Cluster control can be done without the need for lock-LUNs or a quorum server. That just happens to be the way ServiceGuard does it.

Life-Keeper uses SCSI-reservations on the LUNs under its control - however it requires a partition on the LUN to achieve this. This is fine for new clusters - but a real pain for existing ones where you need to migrate (I have a few, and they are large clusters - I have one with 14TB of storage for example).

RSF-1 doesn't - so its a bit more of a challenge. But it does make migration easier.

Not sure about VCS - haven't got that far in my quest for an SG replacement yet.....