Backup running too slow

Hi,

I've scheduled system state backup on Windows server 2008 R2 standard and it's running daily basis..

Backup is scheduled on domain controller and the backup stored on network path.

All of sudden backup is running very slowly. It's taking almost 5 Days to finish a single backup.

When I check the event viewer I found the following warning message

Log Name:      System
Source:        vhdmp
Date:          9/22/2015 6:08:19 AM
Event ID:      129
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A

Description:
The description for Event ID 129 from source vhdmp cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer.

If the event originated on another computer, the display information had to be saved with the event.

The following information was included with the event:

\Device\RaidPort1

Event Xml:
  <System>
    <Provider Name="vhdmp" />
    <EventID Qualifiers="32772">129</EventID>
    <Level>3</Level>
    <Task>0</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2015-09-22T00:38:19.360018000Z" />
    <EventRecordID>158075</EventRecordID>
    <Channel>System</Channel>
    <Security />
  </System>
  <EventData>
    <Data>\Device\RaidPort1</Data>
    <Binary>0F001800010000000000000081000480040000000000000000000000000000000000000000000000000000000000000000000200810004800000000000000000</Binary>
  </EventData>
</Event>

Kindly Help regarding this.

Thanks..