[Linux-cluster] DRBD and redhat cluster

[Arjuna Christensen]

I've been using RHCS to control DRBD quite happily, but only in a active/passive scenario.

All it requires is a little script, and an rgmanager '<script../>' object:

#!/bin/bash
exec /etc/ha.d/resource.d/drbddisk <resourcename> $@

(/etc/ha.d/resource.d/drbddisk is installed by the DRBD package)

Regards,

Arjuna Christensen | Systems Engineer 
Maximum Internet Ltd
DDI: + 64 9 913 9683 | Ph: +64 9 915 1825 | Fax:: +64 9 300 7227
arjuna.christensen at maxnet.co.nz| www.maxnet.co.nz

-----Original Message-----
From: linux-cluster-bounces at redhat.com [mailto:linux-cluster-bounces at redhat.com] On Behalf Of Chris Picton
Sent: Monday, 14 April 2008 4:43 a.m.
To: linux-cluster at redhat.com
Subject: [Linux-cluster] DRBD and redhat cluster

Hi all

I am planning a pair of machines using DRBD to export redundant block 
devices via gnbd

I will have about 10 other machines using gfs2 to access this data.

I have thought of a few different ways of accomplishing this, and would 
appreciate any feedback you may have.

I can run the drbd exports in one of three ways:

1. Single drbd device in single master mode.  The drbd primary resource, 
shared ip address and gndb export will fail over between the two nodes.

Advantages.  Simple setup
Disadvantages.  One machine always fairly idle

2. Two drbd devices on each server.  Server1 will be primary on the one 
device, server 2 will be primary on the other device.  As above, each 
drbd resource will have an associated IP address and gnbd export 
associated with it.  These resources will fail over between the two 
nodes.  The remaining cluster nodes will assemble these using a striped 
clvm.

Advantages.  The two nodes will be equally used.  Will get double the 
throughput from the pair of machines (assuming high speed bonded 
crossover between the two).  Also, will be able to add another pair of 
these machines later to increase bandwidth and storage space for the LVM.
Disadvantages: More complex

3. A drbd device in master/master mode, exported from both via gnbd.  
Cluster members will access this via dm-multipath.  

Advantages: not sure
Disadvantages: Will bandwidth be shared between the two machines?



In addition to the options above, I am also wondering about the cluster 
software I should use.  I will have to use RHCS to use gfs2 and 
fence_gnbd correctly, but is heartbeat a better choice than failover 
domains for the drbd exports?

Any insight will be helpful

Chris

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