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I wanted to check the performance of filesystems of my newly purchased VPS and compare it to the old one, the results surprised me though and I don't know how to analyse them.

I picked bonnie++ to conduct a test using: bonnie++ -d /tmp -u root -r 1024.

Results for VPS #1: 1vCPU, 2GB RAM, KVM, Raid 10 SSD:

Version  1.97       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
vps1        2G  1207  99 552273  58 122473  11  4304  99 183244   8  2234  20
Latency              8463us   16319us     166ms    2585us    9330us   10843us
Version  1.97       ------Sequential Create------ --------Random Create--------
vps1           -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
Latency              5032us     463us     532us     137us      33us     270us

Results for VPS #2: 3vCPU, 4GB RAM, OpenVZ, RAID 10 SSD or PCIe SSD:

Version  1.97       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
vps2            2G   472  99 146096  20 253477  28  1833  99 3544857  99 +++++ +++
Latency             29757us    1423us    1882us    8627us      20us   10162us
Version  1.97       ------Sequential Create------ --------Random Create--------
vps2               -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
Latency               143us     971us     916us     166us      77us      43us

So basically bonnie++ says that:

  • VPS #1 has ~539MB/s write speed & ~179MB/s read speed
  • VPS #2 has ~143MB/s write speed & ~3462MB/s read speed

These results seem highly unlikely to be true, how would the other host achieve 20 times faster read speed?

Am I picking out the wrong columns or interpreting something incorrectly? Am I invoking bonnie++ with wrong parameters? Is there something else that I'm doing wrong?

Results for dd if=/dev/zero of=/root/testfile bs=1G count=1 oflag=dsync:

VPS #1: 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 2.35854 s, 455 MB/s

VPS #2: 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 41.0872 s, 26.1 MB/s

Results for dd if=/root/testfile of=/dev/null:

VPS #1: 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 1.67369 s, 642 MB/s

VPS #2: 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 2.16705 s, 495 MB/s

biphobe
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  • 3.5 GBps is what you get out of a single consumer grade NVMe SSD, so it is possible. Have you tried a different test like hdparm, though? – mzhaase Dec 02 '16 at 13:12
  • @mzhaase Shouldn't write speed be significantly higher then? I tried using `hdparm`, but it doesn't seem to work with `OpenVZ` and `simfs` - I can't find any other tool which would work with `simfs` - could you recommend me something else? – biphobe Dec 02 '16 at 13:33
  • Ah, I see, I would at least try `dd` to see if you get the same ballpark. SSD write speed is always slower, and if it is a VPS, and someone else is writing a lot, it could explain the numbers. You should do these tests multiple times at different times of the day (via cron, for example) and then average the results. – mzhaase Dec 02 '16 at 13:38
  • @mzhaase I have added results from `dd`. So write speed is believable, but what about the read speed of ***VPS #2***? If it's SSD is under heavy stress and write speed goes down to ~26MB/s, shouldn't read speed go down as well? I can't find any other tool than `bonnie++` which would benchmark read speed of filesystem for `simfs`. – biphobe Dec 02 '16 at 14:25
  • You can do `dd if=/root/testfile of=/dev/null` – mzhaase Dec 02 '16 at 14:26
  • @mzhaase I have added the results and I'm getting confused. For `VPS #2` `Bonnie++` reports read speed of `3462MB/s`, `dd` reports `495MB/s`. Which one is the real speed? Are these `dd` commands reliable? Is `Bonnie++` reporting false data? – biphobe Dec 02 '16 at 14:45
  • Repeat these tests a couple times, if you look at the latency as well, it's all over the place. It might just be that other users of the same hypervisor/LUN are doing IO intensive workloads. – mzhaase Dec 02 '16 at 14:50
  • @mzhaase I will, thanks a lot for your help. I will rely on `dd` then as it seems to be more reliable. Can you answer this question so that I could mark your answer as the right one? – biphobe Dec 02 '16 at 14:52

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