Serviceguard NFS Toolkit for Linux Version A.01.03 Release Notes, July 2005

Serviceguard NFS for Linux Version A.01.03 Release Notes
Known Problems and Workarounds
Chapter 1 13
Known Problems and Workarounds
The following describes known problems with the NFS Toolkit and
workarounds for them. However, this is subject to change without notice.
For the most current information contact your HP support
representative.
More recent information on known problems and workarounds may be
available on the Hewlett Packard IT Resource Center:
http://itrc.hp.com (Americas and Asia Pacific)
http://europe.itrc.hp.com (Europe)
JAGae55739: HA NFS and ‘Stale NFS Handle
What is the problem?
Serviceguard relies on LVM to manage its shared storage containing
data and files of applications managed by SG. Just as with other
applications, an NFS instance managed by SG means that the specific
instance is “active” on one node at a time, with all resources available to
that node only (including volume groups configured as a resource for the
NFS package). If the package goes down on node 1, the resources are
released so that the second node can “claim” the resources. The package
is brought up, and the instance is now “active” on node 2. NFS clients
continue to connect to the server, unaware that the server has migrated
from one node to another.
Behavior has changed in Linux kernel 2.6 such that the kernel uses lvm2
with the device mapper to virtualize devices instead of using the actual
physical names. In this implementation, the actual device node for a
logical volume is dynamically created upon vg activation, meaning a vg
that starts out on node 1 but is failed over to node 2 can very easily end
up with a different minor number after fail over. This will result in
clients who connected before the failover getting a “stale NFS handle”.
The volume groups are created with dynamic minor numbers. This
causes NFS problems (‘stale nfs handle’) on the client when the NFS
package is migrated to another node
What is the workaround? There are two ways to address this issue:
• Create the logical volumes with persistent minor numbers.