Cluster Server Installation Guide for Solaris x64 5.0 - Storage ...
Cluster Server Installation Guide for Solaris x64 5.0 - Storage ... Cluster Server Installation Guide for Solaris x64 5.0 - Storage ...
100 Setting up I/O fencingPreparing to configure I/O fencingI/O fencing operationsI/O fencing, provided by the kernel-based fencing module (vxfen), performsidentically on node failures and communications failures. When the fencingmodule on a node is informed of a change in cluster membership by the GABmodule, it immediately begins the fencing operation. The node attempts to ejectthe key for departed nodes from the coordinator disks using the preempt andabort command. When the node successfully ejects the departed nodes from thecoordinator disks, it ejects the departed nodes from the data disks. In a splitbrain scenario, both sides of the split would race for control of the coordinatordisks. The side winning the majority of the coordinator disks wins the race andfences the loser. The loser then panics and reboots the system.Preparing to configure I/O fencingMake sure you performed the following tasks before configuring I/O fencing forVCS:■■■Install the correct operating system.Install the VRTSvxfen package when you installed VCS.Install a version of Veritas Volume Manager (VxVM) that supports SCSI-3persistent reservations (SCSI-3 PR).Refer to the installation guide accompanying the Storage Foundationproduct that you are using.The shared storage that you add for use with VCS software must support SCSI-3persistent reservations, a functionality that enables the use of I/O fencing.Checking shared disks for I/O fencingThe shared storage for VCS must support SCSI-3 persistent reservations toenable I/O fencing. VCS involves two types of shared storage:Data disksCoordinator disksStores shared dataAct as a global lock during membership changes.Coordinator disks are small LUNs (typically three per cluster)See “Setting up shared storage” on page 34.Perform the following checks for I/O fencing disks:■Identify three SCSI-3 PR compliant shared disks as coordinator disks.List the disks on each node and pick three disks as coordinator disks.For example, execute the following commands to list the disks:
Setting up I/O fencingPreparing to configure I/O fencing101■# lsdev -Cc diskTest the shared disks using the vxfentsthdw script.See “Testing the shared disks for SCSI-3” on page 101.Testing the shared disks for SCSI-3Use the vxfentsthdw utility to test the shared storage arrays support SCSI-3 persistent reservations and I/O fencing. Review the guidelines to run vxfentsthdw program, verify that the systems see the same disk, and proceed to test the disks. Make sure to test disks serving as coordinator disks.See “Setting up coordinator disk groups” on page 104.The vxfentsthdw utility has additional options suitable for testing many disks. Review the options for testing disk groups (-g) and disks listed in a file (-f).You can also test disks without destroying data using the -r option.Review these guidelines for using vxfentsthdw■Verify the connection of the shared storage for data to two of the nodes onwhich you installed VCS.Warning: The tests overwrite and destroy data on the disks unless you usethe -r option.■■The two nodes must have ssh (default) or rsh communication. If you usersh, launch the vxfentsthdw utility with the -n option.See “Enabling communication between systems” on page 35.After completing the testing process, remove permissions forcommunication and restore public network connections.See “Removing permissions for communication” on page 109.To ensure both nodes are connected to the same disk during the testing, usethe vxfenadm -i diskpath command to verify the disk serial number.See “Verifying the nodes see the same disk” on page 101.Verifying the nodes see the same diskTo confirm whether a disk (or LUN) supports SCSI-3 persistent reservations, two nodes must simultaneously have access to the same disks. Because a shared disk is likely to have a different name on each node, check the serial number to verify the identity of the disk. Use the vxfenadm command with the -i option to verify that the same serial number for the LUN is returned on all paths to the LUN.For example, an EMC disk is accessible by the /dev/rdsk/c2t13d0s2 path on node A and the /dev/rdsk/c2t11d0s2 path on node B. From node A, enter:
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100 Setting up I/O fencingPreparing to configure I/O fencingI/O fencing operationsI/O fencing, provided by the kernel-based fencing module (vxfen), per<strong>for</strong>msidentically on node failures and communications failures. When the fencingmodule on a node is in<strong>for</strong>med of a change in cluster membership by the GABmodule, it immediately begins the fencing operation. The node attempts to ejectthe key <strong>for</strong> departed nodes from the coordinator disks using the preempt andabort command. When the node successfully ejects the departed nodes from thecoordinator disks, it ejects the departed nodes from the data disks. In a splitbrain scenario, both sides of the split would race <strong>for</strong> control of the coordinatordisks. The side winning the majority of the coordinator disks wins the race andfences the loser. The loser then panics and reboots the system.Preparing to configure I/O fencingMake sure you per<strong>for</strong>med the following tasks be<strong>for</strong>e configuring I/O fencing <strong>for</strong>VCS:■■■Install the correct operating system.Install the VRTSvxfen package when you installed VCS.Install a version of Veritas Volume Manager (VxVM) that supports SCSI-3persistent reservations (SCSI-3 PR).Refer to the installation guide accompanying the <strong>Storage</strong> Foundationproduct that you are using.The shared storage that you add <strong>for</strong> use with VCS software must support SCSI-3persistent reservations, a functionality that enables the use of I/O fencing.Checking shared disks <strong>for</strong> I/O fencingThe shared storage <strong>for</strong> VCS must support SCSI-3 persistent reservations toenable I/O fencing. VCS involves two types of shared storage:Data disksCoordinator disksStores shared dataAct as a global lock during membership changes.Coordinator disks are small LUNs (typically three per cluster)See “Setting up shared storage” on page 34.Per<strong>for</strong>m the following checks <strong>for</strong> I/O fencing disks:■Identify three SCSI-3 PR compliant shared disks as coordinator disks.List the disks on each node and pick three disks as coordinator disks.For example, execute the following commands to list the disks:
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