Consider this test:
Remote Laptop
- connected to DPM server over a WAN VPN
- DPM Remote Agent (DPMRA.exe) installed
- The only protected items are approximately 13 GB of user data
- Protected user data consists of a combination of a few small files from 500kB to 40MB, a 3GB iso, and a 5GB flat file.
- Protected items were initially syncronized over LAN
DPM Server
- DPM 2012 R2 with colocated SQL Server
- Windows Server 2012 R2 Hyper-V Guest
The Test
1. Make any change to the contents of the 5GB flat file, for example, changing the value of one byte.
2. Initiate Syncronization.
3. Measure the amount of data sent from the DPM server to the DPM client. (Important: The opposite direction you'd think the data should go to be backed up.)
My Results
For this test, I measured approximately 13MB sent from the DPM serverto the DPM client. When I increased the flat file from 5GB to 10GB, that measured value increased to 40MB.
This seems like a rather large amplification of data transfer (1 byte changing precipitates tens of MB transferred).
The Question
Why does this happen? How can I avoid it for large flat files?