11.14 Preventing Pools from Activating on Multiple Servers

If enabled, the pool Multiple Server Activation Prevention (MSAP) prevents some accidental activations of a pool on more than one server at a time. It does not catch all multiple activations. You should never purposely attempt to activate a pool on two servers at the same time. MSAP is not meant as a replacement of clustering software that controls shared pools.

MSAP protects pools on systems that do not have clustering installed but are attached to a shared disk by accident. For example, a pool might not be marked with the Shareable for Clustering attribute, but it exists on shared disks seen by multiple servers.

Pool MSAP also protects against dangerous conflicts that can occur if you disable the Shareable for Clustering flag in order to force an activation of a shared pool, or if you use override=shared when activating a pool. If MSAP detects a conflict, it deactivates the pool before massive corruption occurs.

If you unload Novell Cluster Services™ NLM™ software, or if you are not running it, pool MSAP provides an extra level of protection. The clustering software watches pools that are marked with the Shareable for Clustering attribute; MSAP detects conflicting connection from multiple servers and prevents corruption of pools even on devices that are marked as Not Shareable for Clustering.

In some cases, the MSAP software causes pools to take up to 30 seconds to activate. This delay might occur on the next pool activation after the Server ID or the Cluster ID changes for a given server pool. The Server ID changes if the registry is corrupted. The Cluster ID changes if the Cluster eDirectory object ID is lost.

If MSAP is enabled, all active NSS pools are read every 14 seconds. If your storage media are not shared between multiple servers such as in a SAN, you can clear the zpool_feature_msap bit. You should not clear this bit if your pools are on physically shared storage media.

If a pool can be accessed by older servers not running the Support Pack with the MSAP software, then multiple pool activations can still occur.

IMPORTANT:MSAP does not protect against partition conflicts for pools. It does not prevent multiple servers from creating a pool in the same partition.

11.14.1 Managing MSAP Using Server Console Commands

The management file for pool MSAP is _admin\manage_nss\pool\poolname\zlss\msap.xml. One file exists for each pool. The msap.xml file contains MSAP statistics for the pool. The MSAP attribute is displayed in the Enabled Attributes ( <enabledAttributes>) tag of the poolinfo.xml management file.

For manage.cmd, the pool operation getPoolInfo returns the MSAP tag ( <msap>) in the Supported Attributes tag ( <supportedAttributes>) and the Enabled Attributes tag ( <enabledAttributes>).

For APIs, the pool feature zpool_feature_msap can be viewed and controlled using the zGetInfo and zModifyInfo commands.

Syntax

Use the following table understand MSAP console commands.

MSAP Console Command

Description

nss /msapserver

Enables MSAP for all the pools on the server. By default, MSAP is enabled for every pool on the server. We recommend that you never disable MSAP.

nss /nomsapserver

Disables MSAP for all the pools on the server. This command remains in effect only until the server is next rebooted. We recommend that you never disable MSAP.

nss /msaprebuild

Rebuilds a corrupt MSAP block. Before issuing the command to rebuild, you must deactivate the pool because a corrupt MSAP prevents a pool from going into Maintenance state. Rebuilding an MSAP block does not give the rebuilder ownership of the pool.

nss /poolmsap=poolname

Enables MSAP for a given pool on the server. MSAP is enabled the next time the pool is activated. (Enter the command, deactivate the pool, then activate the pool. MSAP is now enabled.)

nss /nopoolmsap=poolname

Disables MSAP for a given pool. Use the command when the pool is activated. MSAP is disabled the next time the pool is activated. (Enter the command, deactivate the pool, then activate the pool. MSAP is now disabled.)

nss /pools

Displays the message “Multi-use detect” for pools that have MSAP enabled.