Online defragmentation affecting server performance

We've been having trouble with our file server lately. Everyday around 5pm it fires an online defrag of the drives that basically tanks the server for 10-15 minutes.

I've attached the event log. Anyone know how I can turn this off or reschedule it to off time?


Event Type:      Information
Event Source:      ESENT
Event Category:      Online Defragmentation
Event ID:      701
Date:            3/23/2011
Time:            5:15:45 PM
User:            N/A
Computer:      FILESRV
Description:
Dfsr (3308) \\.\G:\System Volume Information\DFSR\database_F834_AD53_34AD_1622\dfsr.db: Online defragmentation has completed a full pass on database '\\.\G:\System Volume Information\DFSR\database_F834_AD53_34AD_1622\dfsr.db'.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.