DigiVault is a backup product, not a fail-over system, but because it provides continuous data protection, it has a place in the high-availability scenario. It uses a small agent on each Exchange 2000 or Exchange 2003 server to track all changes to the database. All transactions are recorded as they occur, ensuring no loss of e-mails that have arrived since the last backup. I tested Version 1.4.
Multiple Exchange servers can be protected by one DigiVault repository and be managed from a single console. Backups can be scheduled, but restores are performed manually.
DigiVault requires domain admin privileges to install. The console and the DigiStore vault can share the same system. The DigiStore repository requires enough storage to hold the mail stores for all servers you want to protect. Although the repository is compressed, storage requirements will quickly mount if you keep each version of messages in the store. Archiving can be driven by fine-grain policies, but policy is applied on a per-store basis. You can track every change to some accounts, while keeping only the latest copy of other mailboxes, but only by spreading the accounts across separate stores.
One console is used to manage backups and restores for all servers in the domain. The data store is encrypted using a public/private key. Transmissions to the data store can be encrypted as well, if the store is at an off-site location connected via WAN.
Restores must be performed on unmounted stores, meaning users’ mailboxes must be offline until the recovery is complete. Restores went quite rapidly in my testing, however, with a 1.1GB mailbox restored in less than a minute. Data can be restored to a different server or mailbox, if necessary for auditing purposes. Transactions received since the last backup are backed up before the restore commences.
DigiVault does not provide high availability in the same sense as the other products covered here, but it should be considered as an adjunct for the others, and it may be enough for organizations that can tolerate short periods of unavailability. DigiVault works with Lucid8’s GOexchange product to find and correct errors in the store and rebuild indexes to provide a more reliable environment in Exchange.
Each of these solutions offers benefits and disadvantages, and pricing varies widely. Which is least expensive will depend on how many users per server you have. If yours is one of those organizations that actually manages to support thousands of users per Exchange server, Neverfail’s $7,600 per server pair might be cheaper than Quest’s $8 per user, per year. You’ll also need to look at how many additional servers are required. All but Neverfail can protect multiple Exchange servers with one backup server, Neverfail requiring one backup server for each Exchange server protected.
The degree of automatic protection and impact on the end-user also varies widely. DigiVault requires taking the mail store offline to restore it, and in the event of hardware failure, it requires a complete re-install. It’s intended to protect against data loss, not outages, and it does this well. MailShadow requires admins to initiate a manual switch-over for affected users and requires users to restart Outlook. Quest has automated switch-over for affected users, although Outlook will have to be restarted. Both Neverfail and SteelEye provide automatic fail-over for a whole server, and SteelEye provides additional many-to-one functionality at a lower price.
The best fit for you will depend on the percentage of your user accounts that need to be protected, how many Exchange servers you have to protect, how much you care about having to install an agent on the Exchange server, and whether you regard database corruption as a major threat. Although database corruption is not likely, the process to recover from it can be so terrible that it’s worth additional protective measures, either through a CDP product such as DigiVault or via the transaction-based replication MailShadow and Quest provide.