XADM: Space Requirements for Exchange 5.5 Fault Tolerant Upgrade

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To successfully complete the upgrade process, the computer must have a local disk drive (network drives cannot be used) with free space equal to (or greater than) the size of all three (or four) Exchange Server databases. This disk will be the location of the temporary directory specified during the upgrade process in the Fault Tolerant window. The databases involved in the upgrade are Priv.edb, Pub.edb, Dir.edb, and XDir.edb. XDir.edb exists if MS Mail dirsync has been run against this server. Therefore, before you attempt to upgrade, add the sizes of the Priv.edb, Pub.edb, Dir.edb, and XDir.edb files, and then add 2 megabytes (MB). Verify that the temporary file location that you specify has sufficient free space to ensure that the upgrade can complete successfully.

The Fault Tolerant upgrade defragments each database and places the temporary, defragmented .edb file into the specified directory. Temp is the default directory. After all files have completed the defragmentation process, they are copied to the location of the original .edb files, overwriting the original files. The upgrade process removes the temporary files from the Temp directory. Therefore, if the defragmentation process fails on any of the files, all of the originals are still in place and the upgrade can be aborted.