Is docker file system slow?

Let’s measure how fast file operations are performed in docker:

The diskspd.exe Microsoft tool will generate load:

  • Operate with 2GB file size
  • A few seconds for warming-up and slowing-down
  • Block size of 128K
  • 4 threads
  • Random reads
  • Run test for 2 minutes

diskspd.exe -b128K -d120 -o16 -t4 -r -c2G -w60 -W2 -C2 filepath

No other resource-consuming activities were performed in the system during test.

Test specs

Docker Desktop v.2.2:

Tested docker version

The host Windows version is 1909:

Even though same hardware used inside/outside container, I’ll mention year-old SSD & 8 core CPU hardware used in benchmark.

Results

Surprisingly, local file system is 10 times faster than one sitting inside container:

Results, summarized

Disclaimer: At the moment of the article initial publish, I do not have a solid technical explanation why that happens. Detailed results could be found below.

Baseline: local file system

Outside container, local results

Inside container: exposed volume

Exposing volume outside

Inside container: do not expose volume

Do not expose file system outside container

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