Elephant Outlook uses server clustering to ensure predictable and trustworthy messaging. A server cluster is a collection of servers that together provide a single, highly available system for hosting applications. To manage the high message traffic, Elephant Outlook has implemented a clustering solution that makes Exchange servers at Elephant Outlook available (in terms of global overall availability) more than 99.9% of the time (including both planned and unplanned outages).

Active/passive clustering, the cluster includes active nodes and passive nodes. The passive nodes are only used if an active node fails. In active/active clusters, all nodes are active. In the event of a failover, the remaining active node takes on the additional processing operations, which causes a reduction in the overall performance of the cluster. Active/passive cluster configurations are generally recommended over active/active configurations because they often increase performance, availability, and scalability.

Our SAS drive enclosures are dedicated and directly attached to each mailbox role and to each mailbox cluster node (total of 2 arrays for each cluster pair) to deliver speed, performance and reliability that satisfies demanding server applications as Exchange where data is actively stored and frequently changing.

Each enclosure utilizes multiple RAID controllers that perform the necessary calculations, controls I/O operations, and communications. Given their critical tasking, the enclosures are designed to incorporate twin active/active RAID controllers with mirrored cache for high-availability. If one controller should fail, the surviving controller can handle the full processing load until its mate is brought back online.

All enclosures and storage arrays include Hot Standby drives. The storage processors detect disk failures and automatically switch to the Hot Standby drive and use that drive until repairs are made and the failed drive is replaced.

With redundant arrays of independent disk (RAID), data is spread across multiple drives providing a built in redundancy. RAID increases the data integrity, fault-tolerance, throughput and capacity as compared to single disk systems. This enables the system to automatically recover, without loss of data.

By increasing performance and by striping volume data across multiple disk drives and disk mirroring to duplicate data between two disk drives, Elephant utilizes the high performance RAID 10. RAID provides high availability by combining features of RAID 0 and RAID 1 for fault tolerance optimization.

Cluster continuous replication (CCR) is a high availability feature of Microsoft Exchange that combines the asynchronous log shipping and replay technology built into Exchange 2007 with the failover and management features provided by the Cluster service.
Elephant Outlook’s architecture is designed to provide high availability for Exchange 2007 Mailbox servers by providing a solution that:

• Has no single point of failure
• Has no special hardware requirements
• Has no shared storage requirements
• Designed to be deployed in one or two datacenter solutions
• Can reduce full backup frequency, reduce total backed up data volume, and shorten the service level agreement (SLA) for recovery time from first failure

By using cluster continuous replication, mailbox databases on the active node are continuously and asynchronously updated to a second copy of a database on another node. Log copying and replay are performed continuously.

Data Protection Manager (DPM) provides much more granular protection by combining the Exchange Server transaction log architecture with the block-level synchronization of DPM. Exchange transaction logs are continuously synchronized while changes to disks are tracked to identify which database pages have changes. Change pages are copied to the DPM, where they are applied to an active replica of the data, with previous iterations stored as a set of differences within the preceding backup.

Storage area network (SAN) is a network of shared storage devices, which included our high-availability EMC CX3 Ultra fiber disk arrays and Overland Robotic tape libraries built to prevent any single point of failure.

Elephant's continuity strategy includes vaulting of media libraries. We maintain a scheduled tape rotation in a secure and environmentally controlled off-site facility.

Next: Compliance Journaling & Managed Folders