How to fail over an Exchange database using PowerShell
Update-MailboxDatabaseCopy "DB_NAME\SERVER_NAME" -CatalogOnly
Update-MailboxDatabaseCopy "MB-HO-03\HO-EX2010-MB1" -CatalogOnly
Get-MailboxDatabaseCopyStatus | fl name, contentindexstate
Move-ActiveMailboxDatabase DB_NAME -ActivateOnServer SERVER_NAME -SkipClientExperienceChecks
Move-ActiveMailboxDatabase MB-HO-03 -ActivateOnServer HO-EX2010-MB2 -SkipClientExperienceChecks