Slow WinPE Boot Speed

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slow speed

Default out-of-the-box booting on WinPE with SCCM 2012/2016 is very slow. In some environments I’ve seen this take 3 hours to download the Boot.Wim. This is because System Center Configuration Manager 2012/2016 uses small TFTP block sizes of 512 bytes.

This behavior is set because it’s compatible with all network configurations; but the result is that the PXE boot speed can be very slow using Operating System Deployment with SCCM.

To increase the PXE boot speed, we need to modify TFTP Block Size.
In the registry editor:
Name : RamDiskTFTPBlockSize
Value : 16384 (decimal)

16384 is the maximum supported value.
If it is bigger, you can have corrupted data.
However I recommend to do some test with values :
– 4096,
– 8192,
– 16384.
I typically run 16384 and 8182 in my environments. These will be DP that are on server 2008R2 and later.

Restart the Windows Deployment Services Service. (WDS)

On this particular PXE-DP the time to download the boot.wim increased by roughly 80%

To my knowledge this feature has been built into CB1606 but I have not moved there yet to test myself.

ALSO SEE : Rebuild site servers without redistributing content over the WAN