How do i stop increasing Exchange Database partition space

The exchange database files will not shrink in terms of disk space usage.
You should have white-space (free space) inside the Exchange database files, that will fill up first and when no more white-space is available then the disk usage/file size will start to increase again.
If you look in the application event log for ID 1221 you will see the results of the online defragmentation and it will tell you how much white-space/free-space is available in the Exchange database file.
 

Dear Please find below description of event id 1221,
"The database "First Storage Group\Mailbox Database" has 14701 megabytes of free space after online defragmentation has terminated."

Does it mean "mailbox database.edb" file has 14gb white-space free? It will fill this space first before using the empty disk space. So in my case I have 30gb disk space + 14gb while-space =44gb free space catagorically.

Am i right? please advise.

you are right, it will fill up / use the white-space (14701 MB) first, when that is gone then the disk file space will start to increase.
 

If you only have 1 storage group then you are OK.  If you have multiple storage groups then you need to monitor those as well.  The event 1221 will be displayed for each storage group if you have multiple storage groups.
 

Dears, Appreciate quick response. I have more space on SAN, can I create a 500 partition and move the Database path of my existing storage group to this new partition? please advise.

Also to add if you have event 1221 generated for an mailbox store then you can run an offline defragmentation on that store using eseutil /d command to shrink the database by 14 GB (in your case)

You can move the storage group to a new location/folder/drive.
It will dismount the store, move the files and then remount the store at the new location.  It is all automatic.  

When you move the storage group, use the Exchange System Manager feature, just to be clear on this.
 

Dears, I have exchange 2007 mailbox cluster using SCC on Windows 2003 platform. At first I have to add the new partition as a Cluster Resource, make sure partition accessible from any active node, then Dismount the Storage Group, then move to the new location and then mount the Storage Group. am i right ?

Does this gonna have any consequences, i have around 1200 mailboxes, few very critical mailboxes of managers. I want to be very safe. please advise.

Dears, is it necessary running offline defragmentation on that store using eseutil /d. exchange doesnt consdier it as white-space unless and untill i run offline defragmentation ?