Veritas Storage Foundation 5.1 SP1 Cluster File System Installation Guide (5900-1510, April 2011)

to PROM level with a break and subsequently resumes operations, the other
nodes may declare the system dead. They can declare it dead even if the system
later returns and begins write operations.
I/O fencing is a feature that prevents data corruption in the event of a
communication breakdown in a cluster. SFCFS uses I/O fencing to remove the
risk that is associated with split-brain. I/O fencing allows write access for members
of the active cluster. It blocks access to storage from non-members so that even
a node that is alive is unable to cause damage.
After you install and configure SFCFS, you must configure I/O fencing in SFCFS
to ensure data integrity.
See “About planning to configure I/O fencing” on page 88.
About I/O fencing for Storage Foundation Cluster File
System in virtual machines that do not support SCSI-3
PR
In a traditional I/O fencing implementation, where the coordination points are
coordination point servers (CP servers) or coordinator disks, Veritas Clustered
Volume Manager and Veritas I/O fencing modules provide SCSI-3 persistent
reservation (SCSI-3 PR) based protection on the data disks. This SCSI-3 PR
protection ensures that the I/O operations from the losing node cannot reach a
disk that the surviving sub-cluster has already taken over.
In virtualized environments that do not support SCSI-3 PR, Storage Foundation
Cluster File System attempts to provide reasonable safety for the data disks.
Storage Foundation Cluster File System requires you to configure non-SCSI3
server-based I/O fencing in such environments. Non-SCSI3 fencing uses CP servers
as coordination points with some additional configuration changes to support I/O
fencing in such environments.
See “Setting up non-SCSI3 server-based I/O fencing using installsfcfs” on page 169.
See “Setting up non-SCSI3 fencing in virtual environments manually” on page 180.
About I/O fencing components
The shared storage for SFCFS must support SCSI-3 persistent reservations to
enable I/O fencing. SFCFS involves two types of shared storage:
■ Data disks—Store shared data
See “About data disks” on page 84.
83Preparing to configure SFCFS
About I/O fencing for Storage Foundation Cluster File System in virtual machines that do not support SCSI-3 PR