Physical machines

GCE n1-highcpu-2 machine type

  • 1x dedicated local SSD mounted under /var/lib/etcd
  • 1x dedicated slow disk for the OS
  • 1.8 GB memory
  • 2x CPUs

etcd Cluster

3 etcd 2.2.0-rc members, each runs on a single machine.

Detailed versions:

etcd Version: 2.2.0-alpha.1+git
Git SHA: 59a5a7e
Go Version: go1.4.2
Go OS/Arch: linux/amd64

Also, we use 3 etcd 2.1.0 alpha-stage members to form cluster to get base performance. etcd's commit head is at c7146bd5, which is the same as the one that we use in etcd 2.1 benchmark.

Testing

Bootstrap another machine and use the boom HTTP benchmark tool to send requests to each etcd member. Check the benchmark hacking guide for detailed instructions.

Performance

reading one single key

key size in bytes number of clients target etcd server read QPS 90th Percentile Latency (ms)
64 1 leader only 2804 (-5%) 0.4 (+0%)
64 64 leader only 17816 (+0%) 5.7 (-6%)
64 256 leader only 18667 (-6%) 20.4 (+2%)
256 1 leader only 2181 (-15%) 0.5 (+25%)
256 64 leader only 17435 (-7%) 6.0 (+9%)
256 256 leader only 18180 (-8%) 21.3 (+3%)
64 64 all servers 46965 (-4%) 2.1 (+0%)
64 256 all servers 55286 (-6%) 7.4 (+6%)
256 64 all servers 46603 (-6%) 2.1 (+5%)
256 256 all servers 55291 (-6%) 7.3 (+4%)

writing one single key

key size in bytes number of clients target etcd server write QPS 90th Percentile Latency (ms)
64 1 leader only 76 (+22%) 19.4 (-15%)
64 64 leader only 2461 (+45%) 31.8 (-32%)
64 256 leader only 4275 (+1%) 69.6 (-10%)
256 1 leader only 64 (+20%) 16.7 (-30%)
256 64 leader only 2385 (+30%) 31.5 (-19%)
256 256 leader only 4353 (-3%) 74.0 (+9%)
64 64 all servers 2005 (+81%) 49.8 (-55%)
64 256 all servers 4868 (+35%) 81.5 (-40%)
256 64 all servers 1925 (+72%) 47.7 (-59%)
256 256 all servers 4975 (+36%) 70.3 (-36%)

performance changes explanation

  • read QPS in most scenarios is decreased by 5~8%. The reason is that etcd records store metrics for each store operation. The metrics is important for monitoring and debugging, so this is acceptable.

  • write QPS to leader is increased by 20~30%. This is because we decouple raft main loop and entry apply loop, which avoids them blocking each other.

  • write QPS to all servers is increased by 30~80% because follower could receive latest commit index earlier and commit proposals faster.