[LU-10272] strange time of reading for large file

• Status: Resolved
• Project: Lustre
• Affects Version/s: Lustre 2.4.2
• Type: Bug
• Priority: Minor
• Reporter: Rosana Ribeiro
• Assignee: WC Triage
• Resolution: Won't Fix
• Epic/Theme: Performance
• Severity: 3

Description

In our application, during the performance testing on lustre 2.4.2 we got times of reading and writing to test I/O operations with a file of almost 400GB.
Running this application a lot of times, consecutively, we see that in write operations, I/O time remain on same range, but in read operations there are a huge difference of time. As you can see below:

Write time [sec]:
325.77
318.80
325.44
458.54
316.89
327.75
344.90
340.34
383.57
316.35

Read time [sec]:
570.48
601.11
447.14
406.39
480.44
5824.40
299.40
293.54
1049.93
4190.47

We ran on the single client with 1 process and tested on same infrastructure (hardware and network).
Could you explain why is reading time so distorted? What kind of problem might be occurring?

Comments

[Peter Jones]

Does this behaviour replicate on a more current 2.10.x release?

[Rosana Ribeiro]

I tested at lustre 2.4.2, and unfortunately I do not have how to test this behaviour in a 2.10.x release.
I would like to know why this behaviour in read operation happen with one process and what I can do to change it.

[Peter Jones]

ok then you are better off directing your enquiries either to your Lustre support provider (if you have one) or to the Lustre mailing lists. This project is for tracking issues relating to the upcoming maintenance releases and 2.4.2 is very old and many changes have occurred since that time.