WSL2 io speeds on Linux filesystem are slow

Question

Trying out WSL2 for the first time. Running Ubuntu 18.04 on a Dell Latitude 9510 with an SSD. Noticed build speeds of a React project were brutally slow. Per all the articles on the web I'm running the project out of ~ and not the windows mount. Ran a benchmark using sysbench --test=fileio --file-test-mode=seqwr run in ~ and got:

File operations:
    reads/s:                      0.00
    writes/s:                     3009.34
    fsyncs/s:                     3841.15

Throughput:
    read, MiB/s:                  0.00
    written, MiB/s:               47.02

General statistics:
    total time:                          10.0002s
    total number of events:              68520

Latency (ms):
         min:                                  0.01
         avg:                                  0.14
         max:                                 22.55
         95th percentile:                      0.31
         sum:                               9927.40

Threads fairness:
    events (avg/stddev):           68520.0000/0.00
    execution time (avg/stddev):   9.9274/0.00

If I'm reading this correctly, that wrote 47 mb/s. Ran the same test on my mac mini and got 942 mb/s. Is this normal? This seems like the Linux i/o speeds on WSL are unusably slow. Any thoughts on ways to speed this up?

---edit--- Not sure if this is a fair comparison, but the output of winsat disk -drive c on the same machine from the Windows side. Smoking fast:

> Dshow Video Encode Time                      0.00000 s
> Dshow Video Decode Time                      0.00000 s
> Media Foundation Decode Time                 0.00000 s
> Disk  Random 16.0 Read                       719.55 MB/s          8.5
> Disk  Sequential 64.0 Read                   1940.39 MB/s          9.0
> Disk  Sequential 64.0 Write                  1239.84 MB/s          8.6
> Average Read Time with Sequential Writes     0.077 ms          8.8
> Latency: 95th Percentile                     0.219 ms          8.9
> Latency: Maximum                             2.561 ms          8.7
> Average Read Time with Random Writes         0.080 ms          8.9
> Total Run Time 00:00:07.55

---edit 2--- Windows version: Windows 10 Pro, Version 20H2 Build 19042

Answer 1

Late answer, but I had the same issue and wanted to post my solution for anyone who has the problem:

Windows Defender seems to destroy the read speeds in WSL. I added the entire rootfs folder as an exclusion. If you're comfortable turning off Windows Defender, I recommend that as well. Any antivirus probably has similar issues, so adding the WSL directories as an exclusion is probably you best bet.