Enabling IO fencing

To enable IO fencing:

• Each instance in the cluster must run on a separate node.

• All storage devices (disks) that hold database devices must support the SCSI-3 standard and cannot be partitioned.

  SCSI-3 PGR functionality is available only for a physical SCSI disk device or a virtual disk device exported by a storage area network (SAN). Partitioning such a device at the operating system level does not provide SCSI-3 PGR on each partition. Rather, the SCSI-3 PGR, and thus the fencing support, is shared among all partitions on the device. Adaptive Server cannot fence database devices independently.

  Sybase recommends that you do not create database devices on partitions that use the same device as they cannot be fenced independently.

  The quorum must reside on its own device. Adaptive Server does not allow you to create database devices on the quorum device.

  In addition, if device partitions are used outside the cluster, any fencing performed by the cluster denies access to those other partitions for the external applications or file systems placed on them.

IO fencing is based on a device driver API that is targeted to a specific device driver. The device driver is typically called the fence device. Use operating system commands to create the fence device on each of the nodes running the cluster.

To turn on the enable i/o fencing configuration parameter, enter:

sp_configure "enable i/o fencing", 1

The SCSI-3 PGR feature is platform-dependent, and all devices used by the Cluster Edition should have this functionality. See your operating system documentation for complete syntax and setup information.

As part of the cluster creation process, both the Adaptive Server plug-in and sybcluster let you check that each device is enabled for IO fencing. You can also run the qrmutil utility:

$SYBASE/$SYBASE_ASE/bin/qrmutil