In some Exchange Server 2010 environments the administrator may encounter a situation in which mailbox databases need to be reseeded from a single server in one site to multiple servers in another site.
Consider a scenario where the mailbox database is active in a site with a single mailbox server, and has passive copies in a site with two mailbox servers. The two mailbox servers hosting passive copies need reseeding due to some fault that has occurred.
If the reseed was commenced for both servers it would effectively mean the data was replicated across the WAN twice, which may not be ideal depending on the available bandwidth.
This is because by default the database copy update operation uses the active copy of the database as the source. This would be the case if you ran the Update-MailboxDatabaseCopy cmdlet with only the mandatory parameters.
However if you use the console wizard to perform the operation you’ll notice an option to choose the source for the reseed.
This allows you to perform the reseed more efficiently in terms of network bandwidth by reseeding one server first, and then using that passive copy as the source for the second reseed operation.
This can also be performed using Update-MailboxDatabaseCopy with the -SourceServer parameter, for example:
Update-MailboxDatabaseCopy MB-HO-01br-ex2010-mb -SourceServer ho-ex2010-mb2
An alternative would be to reseed one server first, then move the active mailbox database copy to that server before commencing the second database reseed in that site.