IOMeter testing of Server 2016 Deduplicated Volumes.

Or how I created 2.1TB of Dedupe Chunk store in 5 minutes.

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In the process of generating some test data for another post, I managed to completely fill my 5.6TB storage space in 5 minutes, all due to 1 simple thing. IOMeter. The long story short is that I had my storage space running the Hyper-V aware deduplication so I could test the performance. At the same time I was running IOMeter on that volume to generate performance statistics for anther post, however what I didn’t realize was that Microsoft was inline deduping the testfile that IOMeter generated, and then was randomly reading / writing from. The result. 2.1TB of chunk store, and all of my VMs going paused critical.

screen-shot-2016-12-09-at-8-54-25-pm

Thankfully I was able to expand the volume a little bit, get my VMs online again, and then run the following commands to get everything back under control.

Start-DedupJob -Volume E: -Type Scrubbing -Priority High -Memory 50
Start-DedupJob -Volume E: -Type GarbageCollection -Priority High -Memory 50

The Scrubbing job verifies the Chunks, and the GarbageCollection deletes the chunks that are no longer needed.

This process will take a few hours and is pretty I/O intensive on the disk, but it is the only safe way to properly clear that store without destroying your existing data.