121 lines
4.3 KiB
Markdown
121 lines
4.3 KiB
Markdown
# Filesystem Performance Benchmarking
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Filesystem performance has a big impact on overall GitLab performance,
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especially for actions that read or write to Git repositories. This information
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will help benchmark filesystem performance against known good and bad real-world
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systems.
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Normally when talking about filesystem performance the biggest concern is
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with Network Filesystems (NFS). However, even some local disks can have slow
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I/O. The information on this page can be used for either scenario.
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## Executing benchmarks
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### Benchmarking with `fio`
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We recommend using
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[fio](https://fio.readthedocs.io/en/latest/fio_doc.html) to test I/O
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performance. This test should be run both on the NFS server and on the
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application nodes that talk to the NFS server.
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To install:
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- On Ubuntu: `apt install fio`.
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- On `yum`-managed environments: `yum install fio`.
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Then run the following:
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```shell
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fio --randrepeat=1 --ioengine=libaio --direct=1 --gtod_reduce=1 --name=test --filename=/path/to/git-data/testfile --bs=4k --iodepth=64 --size=4G --readwrite=randrw --rwmixread=75
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```
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This will create a 4GB file in `/path/to/git-data/testfile`. It performs
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4KB reads and writes using a 75%/25% split within the file, with 64
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operations running at a time. Be sure to delete the file after the test
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completes.
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The output will vary depending on what version of `fio` installed. The following
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is an example output from `fio` v2.2.10 on a networked solid-state drive (SSD):
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```plaintext
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test: (g=0): rw=randrw, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=64
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fio-2.2.10
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Starting 1 process
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test: Laying out IO file(s) (1 file(s) / 1024MB)
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Jobs: 1 (f=1): [m(1)] [100.0% done] [131.4MB/44868KB/0KB /s] [33.7K/11.3K/0 iops] [eta 00m:00s]
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test: (groupid=0, jobs=1): err= 0: pid=10287: Sat Feb 2 17:40:10 2019
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read : io=784996KB, bw=133662KB/s, iops=33415, runt= 5873msec
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write: io=263580KB, bw=44880KB/s, iops=11219, runt= 5873msec
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cpu : usr=6.56%, sys=23.11%, ctx=266267, majf=0, minf=8
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IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0%
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submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
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complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%, >=64=0.0%
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issued : total=r=196249/w=65895/d=0, short=r=0/w=0/d=0, drop=r=0/w=0/d=0
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latency : target=0, window=0, percentile=100.00%, depth=64
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Run status group 0 (all jobs):
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READ: io=784996KB, aggrb=133661KB/s, minb=133661KB/s, maxb=133661KB/s, mint=5873msec, maxt=5873msec
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WRITE: io=263580KB, aggrb=44879KB/s, minb=44879KB/s, maxb=44879KB/s, mint=5873msec, maxt=5873msec
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```
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Notice the `iops` values in this output. In this example, the SSD
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performed 33,415 read operations per second and 11,219 write operations
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per second. A spinning disk might yield 2,000 and 700 read and write
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operations per second.
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### Simple benchmarking
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NOTE: **Note:** This test is naive but may be useful if `fio` is not
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available on the system. It's possible to receive good results on this
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test but still have poor performance due to read speed and various other
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factors.
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The following one-line commands provide a quick benchmark for filesystem write and read
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performance. This will write 1,000 small files to the directory in which it is
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executed, and then read the same 1,000 files.
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1. Change into the root of the appropriate
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[repository storage path](../repository_storage_paths.md).
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1. Create a temporary directory for the test so it's easy to remove the files later:
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```shell
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mkdir test; cd test
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```
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1. Run the command:
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```shell
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time for i in {0..1000}; do echo 'test' > "test${i}.txt"; done
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```
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1. To benchmark read performance, run the command:
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```shell
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time for i in {0..1000}; do cat "test${i}.txt" > /dev/null; done
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```
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1. Remove the test files:
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```shell
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cd ../; rm -rf test
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```
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The output of the `time for ...` commands will look similar to the following. The
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important metric is the `real` time.
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```shell
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$ time for i in {0..1000}; do echo 'test' > "test${i}.txt"; done
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real 0m0.116s
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user 0m0.025s
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sys 0m0.091s
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$ time for i in {0..1000}; do cat "test${i}.txt" > /dev/null; done
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real 0m3.118s
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user 0m1.267s
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sys 0m1.663s
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```
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From experience with multiple customers, this task should take under 10
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seconds to indicate good filesystem performance.
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