Fail-over friends keep Exchange chugging
Five disaster-proofers take different tacks to mail server protection
Neverfail is relatively expensive, especially if you have multiple Exchange servers. It is
Click for larger view.
SteelEye LifeKeeper is a server fail-over product similar to Neverfail, but it offers additional flexibility, including scheduling of replication for off-peak hours (or with a 24-hour delay to ensure that store corruption isn’t passed on), compression for replication over WAN links, and one-to-many replication to create multiple copies of a single server.
LifeKeeper can run on any version of Windows 2000 or Windows Server 2003. It supports Exchange 2000 and Exchange 2003, and it doesn’t require identical hardware for primary and secondary servers. The cost is less than Windows Clustering, at $3,280 per pair of servers, and one standby Exchange server can protect multiple active Exchange servers, although capacity planning will be essential in case all the active Exchange servers fail at once. In addition, LifeKeeper supports shared storage between the primary and secondary servers, which can speed up the fail-over process.
For this review, I tested LifeKeeper 5.3. Setting up LifeKeeper is straightforward. You will need to create service accounts, as with the other solutions, but the documentation steps you through the process. Clients get an error message during fail-over, but clients on the LAN will only need to retry the operation -- restarting Outlook is not necessary. As with Neverfail, users connecting via MAPI or Outlook Web Access may need to restart the client to connect to the backup server.
LifeKeeper provides data compression and encryption over a WAN connection, and it can replicate to a local server for fail-over, as well as to a remote server for business continuity. The LifeKeeper GUI can administer all LifeKeeper clusters in an enterprise via a straightforward interface.
LifeKeeper offers features that Neverfail doesn’t, and at a lower price. LifeKeeper’s setup is a little more complex than Neverfail’s, but this is partly because of the additional features. One interesting extra is the ability to fail over from a physical to a virtual server, or vice versa, although most admins will not be comfortable running mail servers in a virtual environment just yet. Unless you already have an investment in other Neverfail clustering technologies, LifeKeeper is a better deal.
Cemaphore Systems MailShadow
MailShadow is not strictly speaking an Exchange fail-over product; more accurately, it’s an Exchange mailbox fail-over product. MailShadow uses the Exchange transaction log to mirror each transaction for designated e-mail accounts on one or more Exchange 2003 servers to a backup Exchange server. If a primary Exchange server fails, or its database is corrupted, the designated accounts can access the backup server instead. Because the replication is based on transactions, no corruption of the Exchange database is passed on to the backup. I tested Version 2.0.