Configuring for High Availability

This section provides instructions to create a high-availability (HA) SANmelody configuration. Storage servers may be paired in an active-active high-availability (HA) configuration to protect against various single points of failure. HA configurations also make it possible to upgrade one member of the HA pair while the other takes over selected functions for mirrored volumes.   

High availability is achieved by configuring synchronous mirror volumes created from two storage servers. Each mirrored virtual volume will be assigned both a primary storage server and a secondary storage server. During normal operations, the primary server fields all I/O requests from the application server for that volume.  It also mirrors updates to the secondary storage server to keep it synchronized in real-time. The secondary storage server only takes over when the primary I/O path for a volume has a failure.

 

The figures below depict basic HA configurations for Fibre Channel and iSCSI. An HA implementation can also be based on a combination of both.

Fibre Channel SAN Connections:     

iSCSI LAN Connections:

SANmelody configureforha fc Configuring for High Availability

SANmelody configureforha iscsi Configuring for High Availability

Figure QSHA1   

Figure QSHA2

 

Before you begin, ensure you have completed all steps as outlined in the Pre-Installation Steps:

  • Ensure that both storage servers have SANmelody software running and are connected to each other over a LAN in order to exchange configuration information and exist in a partnership.

  • For Fibre Channel:

  • The servers must also have one or more Fibre Channel connections (direct or indirect) between them to facilitate the mirroring of data from one server to the other. See Figure QSHA1 above.

  • For iSCSI:

  • The servers must have at least one NIC (for iSCSI use) that is connected either directly or indirectly to the other storage server. See Figure QSHA2 above.

  • Both servers must use the same logon username and password created specifically for SANmelody software.

  • DataCore or other qualified multipathing or HA drivers (e.g., DataCore AP, DataCore MPIO, or Veritas DMP) are installed on application servers that will require HA access to mirrored disk resources being provided by the storage servers. Install them using recommended procedures.  See the DataCore SANmelody Technical Support Web site for qualified DataCore products and Application Server High Availability Products.

To configure the HA partnership:

Establishing an HA partnership consists of two parts. Click on the referenced links in the steps below for more instructions.

  1. Before establishing a partnership, the DataCore Storage Domain Server (DcsSDS) service must be associated with a local administrator account and password. This allows the storage servers to share configuration information. This procedure must be performed locally on both SANmelody storage servers. Refer to Assign a Logon/Password for the DataCore Storage Domain Server Service for instructions.
  2. Creating the partnership between two storage servers. You can create the partnership from either storage server. Refer to Establish an HA Partnership for instructions.

 

After the partnership is created, you will have the ability to add mirrors to existing linear virtual volumes and enable multipathing on the mirrored virtual volumes.

Back to Getting Started.

Related Topics:

About Mirroring and High Availability

Create a Virtual Volume Mirror

Enable Multipathing on Standard Mirrors

Partner Tab-Storage Server Properties

 

Configuring for High Availability