Experimenting with a RAMdisk

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One of the slow operations in the MDT Deployment Workbench is the initial “Update deployment share” process that has to completely generate new Lite Touch boot images.  I always assumed that this was slow due to the amount of I/O being generated by the update process.

Recently, ATI and Dataram released a trial version of their RAMdisk software at https://www.radeonramdisk.com (not that I am endorsing the product – it just happened to come through my Twitter feed and it works on Windows 8), so I had a chance to test the assumption:  What would happen if the temporary storage used by MDT to generate the boot images would be on a RAMdisk?

So I installed the software on my laptop, created a 2GB RAMdisk, and formatted it as an NTFS disk.  First, I “completely regenerated” the MDT boot images without using the RAMdisk.  That process finished in six minutes and 15 seconds (6:15).  Then, to get it to use the RAMdisk, I did the following:

  • Start an elevated command prompt.
  • Set TMP and TEMP to point to the RAMdisk (E:\ in my case).
  • Run “mmc.exe DeploymentWorkbench.msc” from the elevated command prompt, so it inherits the TMP and TEMP environment variable settings.
  • “Completely regenerate” the MDT boot images again.

That looks sort of like this:

image

So what difference did it make?  Well, instead of 6:15, the whole process finished in 4:55.  Not too shabby, about 20% faster, but I expected more.  So why wasn’t it any faster?  Well, it turns out it’s just a case of shifting the bottleneck.  Watching the process using ProcMon and the Windows 8 task manager, I could see that the process was CPU-bound; the RAMdisk utilization was negligible.  Hmm, I guess it’s time for a faster CPU…

The trial software doesn’t support server OSes or more than 4GB of RAM; you have to purchase the full version for that.  Maybe I’ll try that sometime: Imagine a VM where the entire VHD is in a RAMdisk.  I wonder how long that would take…