Factors that affect the duration of email migrations

  • Last updated on: 2016-01-18
  • Authored by: Milton Prado

Accurately determining how much time it takes to migrate email data to Rackspace is difficult because of several factors, including system load, bandwidth, average item size, and source or destination bottlenecks. Migrations of mailboxes that are between 350 MB and 1.5 GB in size typically take up to an hour, and groups of mailboxes can be migrated overnight.

The following sections provide more detail about the factors that can affect how long a migration can take to complete.

Simultaneous mailbox migrations

The migration tool that Rackspace uses, MigrationWiz, has reached speeds of over 1.5 GB per hour per mailbox when connecting to high availability infrastructures. Migrating more mailboxes at the same time allows parallel processing and reduces the duration of your migration.

MigrationWiz can migrate hundreds of thousands of mailboxes simultaneously at no additional cost to you. If you migrate all of your mailboxes at the same time, the migration duration is the time it takes to migrate the largest mailbox.

Network speed

How fast are the source and destination servers connected to the Internet? MigrationWiz is only as fast as the slowest link. MigrationWiz was built to work across even the slowest links, connecting to networks that range from T1 speed to networks that host multiple gigabit connections.

Network latency

The network latency depends on the quality of the connection between the source and destination servers.

Number of mailbox items

Mailboxes with more email messages take longer to migrate. For example, if two mailboxes are the same size but have a different number of items, the mailbox with fewer items migrates faster than the mailbox with more items. The servers talk to each other to introduce each message, so several messages will have more overhead from network chatter than one large message.

MigrationWiz is optimized to reduce network chatter. It has moved over a thousand items in less than a minute in some cases.

Mailbox size

Although the volume of data in a mailbox can affect a migration, the number of items in a mailbox has a much greater impact on the duration of a migration.

Mailbox errors

Errors can occur for a number of reasons, including corrupt items and network outages. MigrationWiz contains automated self-healing technology that can automatically manage errors for you in most cases.


If the source or destination system throttles the amount of data that can be read or written, the migration might not be able to use all the available network bandwidth.

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