Automatic Reseed
Although DAGs are probably the best improvement made to Exchange in terms of availability, not every organization can afford to deploy multiple servers to accommodate database copies. Most of the time, the issue is the extra storage required and not so much the servers themselves. For these organizations, Automatic Reseed in Exchange 2013, or simply AutoReseed, might be a good alternative.
When using DAGs, if the disk hosting an active database copy fails, Exchange fails over that database to another server. Then, an administrator typically replaces the failed disk and reseeds the database back to the server where the failure occurred. Of course, it is assumed that there is no resilience at the storage level, by using either enterprise-level storage or Redundant Array of Independent Disks (RAID), which automatically overcomes this particular scenario.
The sole purpose of AutoReseed is to avoid this situation by automatically restoring database redundancy through the use of...
