The first subsection below describes filesystem issues that must be considered when planning a Linux FailSafe system. The second subsection gives an example of an XFS filesystem configuration on a Linux FailSafe system. The third subsection explains the aspects of the configuration that must be specified for a Linux FailSafe system.
The Linux FailSafe software supports the automatic failover of filesystem including XFS, ext2fs, and reiserfs on shared disks. Shared disks must be either mirrored or RAID storage systems that are shared between the nodes in the two-node Linux FailSafe cluster.
The following are special issues that you need to be aware of when you are working with filesystems on shared disks in a Linux FailSafe cluster:
All filesystems to be failed over must be supported by Failsafe.
For availability, filesystems to be failed over in a Linux FailSafe cluster should be created either on mirrored disks or using a system that supports hardware mirroring of the data such as a RAID storage system.
Create the mount points for the filesystems on all nodes in the failover domain.
When you set up the various highly available filesystems on each node, make sure that each filesystem uses a different mount point.
Do not simultaneously mount filesystems on shared disks on more than one node. Doing so causes data corruption. Normally, Linux FailSafe performs all mounts of filesystems on shared disks. If you manually mount a filesystem on a shared disk, make sure that it is not being used by another node.
Do not place filesystems on shared disks in the /etc/fstab file. Linux FailSafe mounts these filesystems only after making sure that another node does not have these filesystems mounted.
The resource name of a resource of the filesystem resource type is the mount point of the filesystem.
Note: When clients are actively writing to a Linux FailSafe NFS filesystem during failover of filesystems, data corruption can occur unless filesystems are exported with the mode sync. This mode requires that local mounts of the filesystems use the sync mount mode as well. Using sync affects performance considerably.
Continuing with the example configuration from the Section 2.2.2, say that volumes A and B have XFS filesystems on them:
The filesystem on volume A is mounted at /sharedA with modes rw and noauto. Call it filesystem A.
The filesystem on volume B is mounted at /sharedB with modes rw, noauto, and wsync. Call it filesystem B.
Table 2-2, lists a label and configuration parameters for each filesystem.
Table 2-2. Filesystem Configuration Parameters
Resource Attribute | /sharedA | /sharedB | Comments |
|---|---|---|---|
monitoring-level | 2 | 2 | There are two types of monitoring: 1 – checks /etc/mtab file 2 – checks if the filesystem is mounted using stat command |
volume-name | volA | volB | The label of the logical volume on which the filesystem was created. |
mode | rw,noauto | rw,noauto,wsync | The mount options used to mount the filesystem. This is specified the same as the options for the mount command or other filesystems listed in /etc/fstab. |
See Section 3.5, for information about creating XFS filesystems.