[Linux-cluster] Network failure results cluster environment unstable & fragile

Deval kulshrestha deval.kulshrestha at progression.com
Fri Feb 24 04:55:29 UTC 2006


I am struggling to get some help on following configuration. This setup is
intended to put live in a data center for 24 x 7 x365, any issue that makes
my environment unstable is very critical here.



My HA Cluster Setup details


1.	HP DL 360 G4p Server                       2nos.
2.	HP MSA 500 G2 (SAN)                     1nos.
3.	RedHat Enterprise Linux 4 ES  
4.	Red Hat Cluster Suite 4


Server does have a HP SCSI HBA. MSA 500G2 is a scsi based SAN. Both of these
server are connected to SAN using SCSI VHDCI cable. I used a network switch
to establish network connectivity for the server. created a disk array of
three HDD on SAN with two logical volumes than  I have installed RHEL 4
Update 1 on both server(Servers are configured with RAID 1) than installed
all HP drivers and management agents. After server configuration and OS
installation I have installed Red Hat Cluster Suite v 4 on both the machine.


Than I have configured Cluster using Cluster Configuration Manager. Added
member hosts, configured fence device and assigned to member host(HP iLO is
certified as an fence device), Configured Failover domain with node
priority, configured resources such as floating IP address, File System,
Script, than configured service which need to be run in HA mode.


After configuring this I have tested with various scenario HA is working
properly, when ever powered off any machine , services fail over on
available node. 




If network goes off on node1, and service which were not running on node1
are started by node1 with shared storage mount point, which was already
running on node 2 but both of these nodes are not able to communicate to
each other, node2 anyway already running the same service with shared
storage mount point. Because of Fencing both of these nodes try to kill each
other. Both of they got hanged up at "Stoping Cluster manager Services.".In
/var/log/messages, it shows fencing s1, fence successful. 

If we disable fencing than 

If network comes back nodes don't synchronize with each other. Shared
storage mount point is available to both the servers. If they try to access
storage at same storage gives IO errors. Hence this entire setup become very
unstable, fragile.







With Regard


Progression Infonet Pvt. Ltd. 
55, Independent Electronic Modules, 
Sector - 18, Electronic City, 
Gurgaon - 122015

Tel          : - 0124 - 2455070, Ext. 215, Fax: 91-124-2398647
Mobile   : - 98186 -82509 
URL        : - www.progression.com 


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