Is docker file system slow?

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

• Volume exposed outside Windows container & Hyper-V isolation (default for Windows 10 Pro)
• File stored inside container without being exposed
• Local file on host machine without any visualization

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:

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:

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

Inside container: exposed volume

Inside container: do not expose volume