[LU-6663] DNE2 directories has very very bad performance

• Type: Bug
• Resolution: Not a Bug
• Priority: Blocker
• Affects Version/s: Lustre 2.8.0
• Labels: dne2
• Environment: The problem only happens with the contents in an DNE2 directory
• Severity: 2
• Assignee: Di Wang
• Reporter: James A Simmons

Description

With my DNE2 setup I attempted to start some jobs on our test cluster and the job got stuck for hours attempting to run. So I did testing to see what was breaking. A simple md5sum on files showed the problem very easily. For normal directories md5sum on a file came back very fast.

[root@ninja06 johndoe]# date;md5sum ior;date
Fri May 29 10:08:24 EDT 2015
4ba1b26f0a4b71dccb237d3fd25f3b67 ior
Fri May 29 10:08:24 EDT 2015

But for DNE2 directories I saw this:

[root@ninja06 jsimmons]# date;md5sum simul;date
Fri May 29 10:08:38 EDT 2015
9fef8669fb0e6669ac646d69062521d3 simul
Fri May 29 10:09:59 EDT 2015

This is not a issue for stats. So it only appears when accessing data from a file. An ls -al on the file simul comes back very fast. I did this test without the work from LU-3534 and the problem still exist.

Issue Links

• is related to: LU-6724 Downgrading from 2.8 with DNE2 patches to 2.5 servers fails: unsupported read-only filesystem feature(s) 2
• is related to: LU-3534 async update cross-MDTs