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Exchange database suddenly shrank 100 GB, what happend?

Can asked
Hi all,

The disk where the exchange databases are located at had only af few GB of free space. So i extended the disk from 1.75 TB to 1.8 TB. I had 50 GB free space after extending the disk.

A day after extending the disk, i noticed i had 150 GB of free space on the same disk. What could happen that the exchange databases suddenly shrank 100 gigs?

Thanks in advance!
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Dr. KlahnPrincipal Software Engineer

Did you change the restore point size allocation while resizing the disk?

If I remember correctly, the Windows default is to allocate 10% of the disk to restore points.  It would be easy to recover quite a lot of disk if the restore point allocation was changed, or if restore points were disabled for that drive.

Perhaps ask the other IT staffers if somebody did an offline Exchange compression on that drive (though at 9GB/hour, I'm sure somebody would have noticed this.)

But what it sounds like is there was something fairly large other than the Exchange database on that drive before, and now it is no longer there.
Peter HutchisonSenior Network Systems Specialist

Does the event logs share any light? Usually Exchange will do online maintenance regularly including database defragging, but not database shrinks as that has to be done manually.
CanSystem Administrator


Thanks for you reply's

@Dr.Klahn: Windows System Restore is a workstation operating system feature (e. g. Windows 7) and as such is not found on any of the Microsoft Server Operating Systems. Other IT staff didnt touch the server aswell. The only files i have on this disk (not the os disk) are exchange databases.

@Peter Hutchison: No, i cant find any usefull info in eventvwr.

Its driving me nuts cause i need to expain where the 100 extra gigs came from.. 
EE Solution Guide - Technical Dept Head
Most Valuable Expert 2017
Did yuo run backup.
If yes Exchange known backup will flush the logs.
CanSystem Administrator


Thank you for your reply MAS,
Yes. Every night there is a backup of those databases.