Filesystem Performance Benchmarking

Filesystem performance has a big impact on overall GitLab performance, especially for actions that read or write to Git repositories. This information will help benchmark filesystem performance against known good and bad real-world systems.

Normally when talking about filesystem performance the biggest concern is with Network Filesystems (NFS). However, even some local disks can have slow IO. The information on this page can be used for either scenario.

Write Performance

The following one-line command is a quick benchmark for filesystem write performance. This will write 1,000 small files to the directory in which it is executed.

Change into the root of the appropriate repository storage path.
Create a temporary directory for the test so it's easy to remove the files later:
```
mkdir test; cd test
```

Run the command:

time for i in {0..1000}; do echo 'test' > "test${i}.txt"; done

Remove the test files:
```
cd ../; rm -rf test
```

The output of the time for ... command will look similar to the following. The important metric is the real time.

$ time for i in {0..1000}; do echo 'test' > "test${i}.txt"; done

real	0m0.116s
user	0m0.025s
sys	0m0.091s

From experience with multiple customers, the following are ranges that indicate whether your filesystem performance is satisfactory or less than ideal:

Rating	Benchmark result
Best	Less than 10 seconds
OK	10-18 seconds
Poor	18-25 seconds
Very poor	Greater than 25 seconds