A practical estimation of the Exchange mailbox migration speed

Featured article by Steven Smith, Independent Technology Author

The typical question asked by clients in any mailbox migration planning workshop is – How much time it will take?. And the common answer from migration specialists is a casual ‘It will be done just as fast as you want’. But wouldn’t it be better for everyone if we could be a bit more specific here?

Before we go into finding out how, let’s try to understand why answering the question accurately is important to you – apart from the obvious reason that you need to provide a quote to the client. If you get to implement the project, you will need project milestones to measure your progress and if at any time in future it appears that you are moving slower than anticipated you can use all available means to rectify this before it spirals out of control.

In the mailbox migration speed calculation two factors are most vital. The first is the infrastructure related stuff like network bandwidth, memory, server speed etc. The second is the human factor i.e. how well trained the end user is? How mentally prepared the management is? How skilled the technical staff is? And so on.

The major tasks that any Exchange Server migration project includes are:

* Migrating Mailboxes and Public Folders

* Migrate mailboxes and public folders’ permissions and properties

* Global Address List synchronization

* Updating/migrating Outlook rules

In the above list, the first task is the one which hinges mainly on the infrastructure part, the rest of them depend on the human factors which we have been previously stated.

Sticking to the scope of this blog, let’s focus on the first factor which is the infrastructure part.

To keep things simple, let’s say there are 100 users in the organization and the average mailbox size is 2 GB for each mailbox. Thus the total size of the mailbox data is 200 GB.

To then measure the speed of migration, migrate a single mailbox from the source to the target Exchange. Next do a size by time calculation and let’s say you arrive at the conclusion that this throughput is 5 GB per hour.

So the total time of migration for these mailboxes will be 200 GB /5 GB/Hr = 40 Hr. But this is just a back of the envelop calculation. In actual production environment, there are many things that matter as the mailbox data may consist of emails with rich graphical content, attachments, calendar items etc. which may take a little more time than in your lab environment. Hence, any pre-migration speed calculation must be done with realistic data.

Based on past experiences, I can say that this is just a theoretical estimation of the migration speed, the actual calculation of migration time must take into account all other tasks related to Exchange migration and not just the data move.

In this context, let me introduce a mailbox migration application that can do all the tasks mentioned above – LepideMigrator for Exchange. The most important thing with this solution is that it can use other network computers’ resources to expedite the data migration part wherein most Exchange administrators find themselves helpless because they don’t want to purchase extra resources just for the sake of expediting migration and it is not something which can be improved by user training or imparting technical knowledge. Exclusive tools are made to meet exclusive requirements and LepideMigrator for Exchange is one of these tools.