How much disk space do you need to reserve for Exchange Server transaction logs?
The required disk space depends on how many logs per day (or week or month) the workload on your server generates. Exchange transaction logs have a fixed size (5MB), so you can easily estimate how many logs will fit into a given amount of space. Simply divide the space by 5,242,880 (1024 x 1024 x 5, or exactly 5MB). Because online and Microsoft Volume Shadow Copy Service (VSS) backups truncate the log files, you probably don't need a huge amount of space available. You need enough space to allow for log accumulation between backups, plus a reasonable reserve. Most servers will generate no more than a few hundred log files per day. You can easily see how many are generated on a typical day by performing a full or incremental backup waiting for a day, then counting the number of generated logs.