When we talk about migrating Public Folders, and believe me I talk about that a lot, the usual assumption is that the migration is to Exchange Online. That is true most of the times, but not all.
BitTitan MigrationWiz is a tool that adapts to all sorts of scenarios, the rule being if you have an Exchange 2007+ in the source and destination, and that of course includes Exchange Online, that MigrationWiz will be able to migrate your Public Folders. That being said I find myself discussing scenarios such as migrating Public Folders from Exchange on premises or Exchange Online, to a destination Exchange On Premises.
For those used to migrate Public Folders into Exchange Online, you would know that one of the main things to take into account is the volume of data to be migrated and how to make that work seamlessly, since the Public Folder mailboxes in Exchange Online have quotas you can’t change, as you can see here.
One of the things that makes MigrationWiz such a good tool to migrate large volume of Public Folder data, into Exchange Online, is that we will automatically split the Public Folder data into multiple mailboxes, therefore preventing a migrate failure and delay if one of the mailboxes gets full during the migration. This is done via support and explained in all the relevant migration guides, such as this one.
So the question now is, would this process be necessary when the destination are Exchange On Premises 2013+?
Answer: No. You can’t change Public Folder mailbox quotas in Exchange Online, but you can change them in Exchange On premises, so you don’t need to automatically split the data into multiple destination mailboxes.
And should I use a single On Premises mailbox for a large volume of data?
Answer: You can, but you shouldn’t. If you have 100, 150 or 200GB of Public Folder data, then yes a single mailbox approach seems reasonable, but if you have more than that you should think about having multiple mailboxes, for reasons like backup and restore management, among others. Another reason for having multiple Public Folder mailboxes might be if you have a multi region Exchange Organization and you want to provide localized access to Public Folders.
Why do you reference the destination as being Exchange 2013+?
Answer: Because this blog post focuses specifically in modern public folders (mailbox vs database).
Now lets have a look at a Public Folder mailbox in Office 365:
As you can see above the quotas are well defined and cannot be changed.
How does that look in Exchange On premises?
Above you can see 2 Public Folder mailboxes. One comes with the quota set to unlimited, which is the default when you create a new Public Folder mailbox in Exchange 2013, and for the other one I’ve set the limits to 150GB, with the following command:
Set-Mailbox -PublicFolder <mailboxname> -ProhibitSendReceiveQuota 150GB -ProhibitSendQuota 150GB -IssueWarningQuota 150GB -UseDatabaseQuotaDefaults $false
Note: Don’t forget to set the database quota defaults to false, if you want the new quotas to apply at the mailbox level.
As you can see above there are differences between Exchange Online and On Premises, and the control you have over both. Consider them when planning your migration.