What is the best practice for cluster lock disk?

[Ganesan R]

Hi,

Can cluster lock disk be part of any activated VG? can be part of cluster package VG? or should it be seperate shared disk?

what is the best practice to create cluster lock VG and cluster lock disks?
like should require seperate VG?..

Many thanks in advance..

[Luk Vandenbussche]

Use a disk which is part of VG in the cluster.

Specify a SECOND_CLUSTER_LOCK disk to obtain a higher availability

[Ninad_1]

Hi,

A lock disk may be used for clusters up to and including four nodes in size. The cluster lock disk is a special area on an LVM disk located in a volume group that is shareable by all nodes in the cluster. When a node obtains the cluster lock, this area is marked so that other nodes will recognize the lock as "taken."

The lock disk is not dedicated for use as the cluster lock; the disk can be employed as part of a normal volume group with user data on it.

Please refer the section in the manual Managing SG pointed by the following url for more info on cluster lock disk.
http://docs.hp.com/en/B3936-90079/ch03s02.html#d0e2149

Regards,
Ninad

[Geoff Wild]

The cluster lock can be part of any shared disk.

It can be part of a shared vg.

You don't need a separate vg for cluster lock.

See the docs on http://docs.hp.com/en/ha.html for more info...

Rgds...Geoff

[Chauhan Amit]

Cluster Lock Disk: This is a shared disk that both nodes can see and that is controlled by LVM.
In a cluster of more than four nodes, a cluster lock disk is not supported or allowed. A quorum server is.

Quorum Server: This is a separate node, not part of the cluster but contactable over a network interface (preferably on the same subnet to avoid delays over routers, and so on). This machine could be something as simple as a workstation running HP-UX 11.0 or 11i (either PA-RISC or IPF), or it could even be a machine running Linux. The Quorum Server listens to connection requests from the Serviceguard nodes on port #1238. The server maintains a special area in memory for each cluster, and when a node obtains the cluster lock, this area is marked so that other nodes will recognize the lock as "taken." It may provide quorum services for more than one cluster.

-Amit

[Chauhan Amit]

Another important point is :

ServiceGuard does not provide a way to specify alternate links to a cluster lock disk.

When you use a virtual disk (VDisk) as your lock disk in an HP 9000 clustering environment, the HP-UX node cannot access the lock disk when both of the following situations apply:
The path that is defined for the FIRST_CLUSTER_LOCK_PV variable is unavailable.
A 50-50 split in the quorum occurs.
To resolve this issue and to maintain redundancy, specify a different path to the lock disk for each HP-UX node in your cluster using the FIRST_CLUSTER_LOCK_PV variable in the cluster configuration ASCII file. For example, if you are configuring a two-node HP-UX cluster, set the path of FIRST_CLUSTER_LOCK_PV on HP-UX server A to the first SAN Volume Controller node (through one fibre-channel switch) and set the FIRST_CLUSTER_LOCK_PV for HP server B to the second node (through another fibre-channel switch).


-Amit

[A. Clay Stephenson]

I suspect that best practice is not to use them but instead use a Quorum Server. A little PC running Linux makes a dandy qs.

[Ganesan R]

Thanks for your replies..

can i use a disk from cluster VG(using for cluster package) for cluster lock? or should it be in non-cluster VG?

Many thanks in advance

[Chauhan Amit]

Hello,

can i use a disk from cluster VG(using for cluster package) for cluster lock? or should it be in non-cluster VG?

Disk has to be from Cluster VG for cluster lock , so that it is visible from both the nodes.

-Amit

[Chauhan Amit]

Another important point regarding power circuit:

It is recommended that you use a single lock disk. A single lock disk should be configured on a power circuit separate from that of any node in the cluster. For example, it is highly recommended to use three power circuits for a two-node cluster, with a single, separately powered disk for the cluster lock. For two-node clusters, this single lock disk may not share a power circuit with either node, and it must be an external disk. For three or four node clusters, the disk should not share a power circuit with 50% or more of the nodes.

-Amit

[Chauhan Amit]

The lock disk is not dedicated for use as the cluster lock; thus, it can be employed as part of a normal volume group with user data on it. The usable space on the disk is not impacted; the lock disk takes no space away from the disk's volume group. Further, the activation of the volume group on one node does not affect the ability of another node to acquire the cluster lock.

I hope it clarifies ur query.

-Amit

[Ganesan R]

Hi Amit,

Thanks for your response.

My Question is,

It has to be from cluster package VG? or it can be?

For examaple, I have a VG on shared storage and it is not being used for any cluster applications.It is activated on one node and being used for some other purpose. but the disks on the vg's are visiable from all the nodes.

can i use a disk from this VG?

Many thanks in advance..

[Chauhan Amit]

HI Ganesan,

You can use Disk from this VG.

-Amit

[Arunkumar.B]

Hi Ganesan,

You can use any pv from any VG.But that PV should be in shared Storage & it should be visible from both nodes..Even if you don't have Cluster lock your cluster will run.But once in 45 mts it will generate error msg in syslog.But if any Cluster tie breaker happens that time ur Entire cluster will down


With Cheers
Arunkumar.B

[Ganesan R]

Hi Gurus,

Thanks for all your responses

[Ganesan R]

Many thanks to all cleared my queries..