Managing Serviceguard NFS for Linux, July 2007

Serviceguard NFS for LINUX Introduction
Overview of the NFS File Lock Migration Feature
Chapter 18
Overview of the NFS File Lock Migration
Feature
The following describes the File Lock Migration feature, which is part of
the NFS toolkit starting with version A.02.00:
• Designate a unique holding directory as part of the NFS package
located on a shared filesystem. In other words, an empty directory is
created on a shared filesystem that moves between servers as part of
the package. This holding directory is a user configurable parameter
(NFS_FLM_HOLDING_DIR in hanfs.conf) and must be dedicated to
hold the Status Monitor(SM) entries only.
• The script, nfs.flm, periodically copies the Status Monitor entries
from the /var/lib/nfs/sm directory on SLES and
/var/lib/nfs/statd/sm directory on RedHat into the package
holding directory. The default for nfs.flm is to copy every five
seconds. This value can be changed by modifying the
PROPAGATE_INTERVAL parameter in hanfs.conf.
• Since the holding directory resides on a shared filesystem, on
failover, it transitions from the primary node to the adoptive node
defined by the NFS package. Once the holding directory is made
available on the adoptive node, the SM entries residing in the
holding directory are copied to the SM directory on the adoptive node
(/var/lib/nfs/sm on SLES and /var/lib/nfs/statd/sm on
RedHat). This sequence of actions sync the adoptive server's SM
directory with that of the primary server. Two NFS packages cannot
run on the same node when lock migration is used. See the
limitations in the next section.
• After failover, the NFS package IP address is configured on the
adoptive node, and sm-notify on SLES and rpc.statd on RedHat is
restarted using package IP. Restarting this daemon triggers a crash
recovery notification event, whereby sm-notify/rpc.statd sends
crash notification messages to all clients listed in the sm directory.
• Any client that holds NFS file locks against files exported by the
NFS package sends reclaim requests to the adoptive node (where the
exported filesystems currently reside) and reclaims its locks.