Bump the size of your information store to 75GB

You've probably read by now that Exchange 2003 Service Pack 2 increases the message store size limit to 75GB on the Standard Edition.  This is a good thing for many smaller IT shops that do not need the other functionality provided by Exchange Enterprise but that are running out of available space in the information store.

After you install Service Pack 2, you might expect an almost fivefold increase right away, but if you look closely, you'll see that the size of your information store is only 18GB--far from the promised 75GB! What gives?

Believe it or not, this is a good thing.

In Service Pack 2, the Exchange developers have provided you with the ability to size the information store to any size you like between 1 and 75 GB, and they chose 18GB as the default (16GB + about 10 percent for a warning buffer). 

The reason: Not everyone has disks on their Exchange server that could accommodate a 75GB information store.  For these users, increasing the store limit all the way to the maximum allowed could result in the Exchange server exhausting its storage resources before getting anywhere close to a maximum.

To change the size limit:

1. Start the registry editor.
2. Browse to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
   Services\ MSExchangeIS\[ServerName]\[GUID of private store] or HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
   Services\ MSExchangeIS\[Servername]\< GUID of public store>3Choose Edit > New > DWORD Value.
3. Name the new value "Database Size Limit in GB"
4. Edit the new value and give it a size between 1 and 75 GB.
5. Restart the Information Store service.

This key will also work on the Enterprise Edition of Exchange if you want to limit the size of a database to less than 8TB. If you ever have to recover Exchange with the /disasterrecovery switch, you will need to manually recreate these keys.