Database availability group. A database availability group is a set of mailbox servers that use continuous replication to update database copies, communicate to manage failures that affect individual databases, and can provide automatic recovery from a variety of failures (at the disk, server, and datacenter levels).
Database-level failover. Exchange Server database availability groups provide automatic failover at the database level without the complexity of traditional clustering. A database-level disruption, such as a disk failure, no longer affects all users on a server. Because there is no longer a strong tie between databases and servers, it is easy to move between database copies if disks fail. This change, coupled with faster failover times (as little as 30 seconds) can dramatically improve your organization’s overall uptime.
Improved site resiliency. Exchange Server database availability groups make it easier to implement site resilience. They simplify the process of extending data replication between datacenters for site failover. The solution, built into Exchange 2010, can now be used to manage both on-site and off-site data replication and mailbox servers. Database copies can be deployed incrementally to meet the specific availability needs of your organization. Log files can be encrypted for greater security, and can also be compressed to improve transmission time and reduce network bandwidth usage.
Easier deployment. You can add high availability to your Exchange environment after deployment without reinstalling Exchange. For smaller sites, you can deploy a simple two-server configuration that provides full redundancy of mailbox data along with Client Access and Hub Transport roles. These changes put high availability within the reach of organizations that once considered it impractical.
Integrated administration. All aspects of high availability administration are handled within Exchange, so you don’t have to manage failover clustering separately in Windows Server, so your environment is easier to manage.
Built-in mailbox recovery. Your organization can rely on the Exchange 2010 high availability infrastructure—which can provide up to sixteen replicated database copies—rather than tape backups to recover from failures, which helps you to reduce operating costs.
Transport resiliency. Transport servers in Exchange 2010 feature built-in protection against the loss of message queues that result from disk or server failure. Servers retain a shadow copy of each mail item after it is delivered to the next hop inside your organization. If the subsequent hop fails before the mail is successfully delivered, the message is resubmitted through a different route.
Online mailbox moves. You can move mailboxes between databases without taking your users offline. Your users can connect to their mailboxes, sending and receiving mail, while the move is taking place. This reduces user downtime, and lets your administrators perform system maintenance during business hours instead of nights and weekends.
Storage IO reductions. Exchange 2010 delivers up to a 70 percent reduction in disk IO over Exchange 2007, and a 90 percent reduction in disk IO over Exchange 2003. So more disks meet the minimum performance required to run Exchange, driving down your storage costs.
Optimizations for SATA disks. IO patterns are optimized so that disk writes do not come in bursts. These optimizations remove a barrier that had previously limited the use of Serial Advanced Technology Attachment (SATA) hard disk drives.
Automatic page restore. Exchange 2010 is more resilient to storage problems. When minor disk faults cause corruption, Exchange can automatically repair the affected database page by using a copy of the database that is configured for high availability. With automatic detection and repair of data corruption from minor disk errors, you can take advantage of lower-cost storage options while you maintain system reliability.
JBOD support. Exchange 2010 can be deployed with up to sixteen replicated copies of each mailbox database, and fast database-level failover makes it possible for your administrators to swap failed drives with minimal impact to your users. Exchange can also automatically repair database pages affected by minor disk faults by using a copy of the database that is configured for high availability. These application-level redundancy features allow RAID-less (JBOD) storage configurations to be used, which can result in dramatic cost savings.
