Secondary backup methods that run against an Exchange server and back up individual mailboxes and messages were popular with Exchange Server 5.5. However, this process was time consuming because, although there often were only 16 GB of email on the server, back up to disk was not widespread and backup tapes were both slow and of low capacity. This procedure -- known as a brick-level backup -- was notorious for slowing the server to a crawl, issuing false messages about store or mailbox corruption and taking all night to complete.
Most third-party backup products take a single pass at the information store level and virtually mount the backup to recover single messages as well as mailboxes and public folders. Although this reduces the backup window, it doesn't reduce the volume of disk or tape that the backups consume.
Using a storage area network (SAN) and the intelligent software configuration within platforms such as snapshot backups and cloning is preferred. However, there are some situations in which a SAN won't be deployed. There also are situations in which a SAN doesn't have the proper or most cost-efficient software to provide the space-efficient recovery needed. There are several applications on the market for the entire Microsoft infrastructure, and Exchange Server specifically, that deliver SAN-quality backups and restores to DAS-based users.
DigiVault from Lucid8 uses a continuous data-protection technique. Once configured, DigiVault constantly backs up the Exchange server and secures information to another source -- either another area on a basic SAN or on disks attached to the DigiVault repository server. Information within the Exchange server is backed up nightly, constantly protected and can be restored relatively quickly.
When combined with Lucid8's DigiScope interface, an Exchange administrator can restore Exchange information from the backups more granularly. The overall volume of disk space that the backups use may not be reduce dramatically; however, the time required to restore an Exchange information store is cut from several hours to about an hour.
AppAssure's Replay for Exchange takes an entirely different approach. Backing up Exchange information stores isn't enough. The size of the Windows installation and the time that it takes to install new copies of Windows and Exchange Server before recovering them is a serious factor, especially in the event of a server failure. Replay protects the entire server at the volume block, instead of the file level.
Like DigiVault, Replay for Exchange monitors disks continuously and secures the information from changed disk blocks to the Replay repository on a set schedule. If the Exchange Server, a domain controller or a BlackBerry Enterprise Server (BES) fails, a new system can be booted using a preboot execution environment (PXE) onto an appropriately configured network. Replay for Exchange will stream the entire operating system, Exchange installation and Exchange databases to the new server. When Replay initiates its first Exchange server backup, it secures every block on the drive containing the databases. Replay will also verify the backup by performing its own type of eseutil operation on the stores.
When Replay performs the second backup, only changed blocks are transferred to the repository. Because the product detects that the original backup is valid, it only needs to validate the integrity of the blocks it secured. Therefore, mid-day database verification is achieved first; verification on a server other than the active Exchange server is achieved next.
This entire process happens very quickly -- shortening the restore process to minutes. The Exchange server comes up in a consistent state, so there is no need for Exchange to conduct any recovery against the stores. This concept also applies to a Replay-protected domain controller and BlackBerry Enterprise Server.
About the author: Mark Arnold, MCSE+M and Microsoft MVP, is Principal Consultant with LMA Consulting LLC, a private messaging and storage consultancy based in Philadelphia, Penn. Mark assists customers in designs of SAN-based Exchange Server implementations. He has been a Microsoft MVP in the Exchange discipline since 2001, contributes to various Microsoft-focused technology websites, and can be found in the Exchange newsgroups and other Exchange forums.
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