High Availability

HA design for a software application protects single points of failure (SPOFs). A SPOF is a critical component of an application whose failure can cause service outage for users. The server-side architecture of SAP BusinessObjects BI Platform consists of five tiers: web, management, storage, processing, and data. (For details, see the administrator’s guide on the SAP BusinessObjects Business Intelligence Platform website.) SAP BusinessObjects BI Platform 4.x provides HA of platform services using CMS clustering, which could provide customers with the required level of redundancy. CMS servers are in the management tier.

SAP BusinessObjects BI Platform tiers are designed as follows to eliminate SPOFs and to provide redundant installation options for native, highly available components:

• Management tier: Includes the CMS servers, event servers, and associated services. SAP BusinessObjects BI Platform cannot function without a CMS server. Multiple CMS servers can run in a cluster on different machines. A cluster consists of two or more CMS servers working together on a common CMS system database. The CMS is a SPOF, so you must create a cluster of CMS servers running in more than one Availability Zone for a highly available design.

• Storage tier: Includes input and output file repository servers. Install these servers redundantly so that failure of any single server doesn’t cause a service outage. The file system used by these servers to store files such as documents, reports, and universes must be on a shared file system. This file system is a SPOF and therefore must be highly available.

• Web tier and processing tier: These tiers perform functions like receiving and processing user requests. These tiers are not SPOFs. However, if a server that provides a specific service isn’t available, users cannot use that service. To avoid such situations, install these servers redundantly so that the failure of any single server doesn’t cause a service outage.

• Data tier: Consists of the CMS system database and the auditing data store. The CMS database is a SPOF. Install a highly available database using vendor-specific database HA technologies. The specific method used depends on the type of CMS database you’re using.

HA Testing

SAP Note 1229417 provides four tests you must perform to ensure that the CMSs are clustered correctly and that cluster functionality is working. Additionally, when performing the tests, you must also ensure that your deployment can tolerate Availability Zone failure. You can confirm this by stopping all the servers in one Availability Zone and making sure that all the services are still available. To test the CMS database, you can perform the failover manually. In the Amazon RDS console, choose Instances, Instance actions, Failover. After all servers in one Availability Zone are shut down and database failover is complete, test the availability of the system and all the services. Repeat the same test for the second Availability Zone.