Hp StoreVirtual 4000 Storage User Manual download pdf (Page 18)

Using the Primary Site designation in two-site configurations

The Multi-Site SAN software supports designating a particular site as Primary so that it does not

go offline when the secondary site goes offline, or when the network link between sites goes offline.

This is specific to the two-site configuration where, without this designation, there would be no way

for the system to determine which site should remain online in the event of a network separation

(classically known in the clustering/distributed systems world as a “split-brain” system).

To set up this type of configuration:

1. Designate one of the sites as primary.

2. Start a majority of managers in the primary site.

Contact Customer Support for more information.

Failure modes and recovery steps

In general, there are three failure modes that a configuration like this can encounter that you should

be aware of. “Failure conditions and resolutions” (page 18) summarizes the failure conditions and

what you should do to rectify the issue.

Table 5 Failure conditions and resolutions

Resolution stepsFailure condition

None. The primary site will continue to operate.Secondary site offline

None. The primary site will continue to operate.Network link between sites fails

Primary site offline 1. If any of the storage systems running managers in the primary site

can be brought back online, you should do this first.

2. If all storage systems in the primary site are lost forever, you can use

the Recover Quorum command-line function to recover quorum in the

secondary site manually. For more information, see “Recover quorum

operation,” next in this section

Recover quorum operation

The Recover Quorum function is introduced with the Multi-Site SAN as a way to bring volumes

back online in the event that quorum in the management group is lost.

CAUTION: The Recover Quorum function should only be used as a last resort. The failed site

must be completely failed to use Recover Quorum safely on the remaining site.

The Recover Quorum command-line function performs the following actions:

1. Removes all offline managers from the management group.

2. Ejects all offline storage systems from the management group.

3. The SAN/iQ software is modified to prevent any data integrity issues in the event any of the

offline storage systems are brought back online.

Best practices for configuring quorum and managers in a Multi-Site SAN environment

Configuring the appropriate number of managers in a Multi-Site SAN on the appropriate storage

systems is an important part of setting up the Multi-Site SAN for high availability and fault tolerance.

“Common Multi-Site SAN configurations with recommended managers” (page 19) identifies

common Multi-Site SAN configurations and the recommended manager configurations.

18 Designing a Multi-Site SAN

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Hp StoreVirtual 4000 Storage User Manual Page 18