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Bug #23235

The randomness of the hash function causes the object to be inhomogeneous to the PG.The result is that each OSD utilization ratio is uneven.

Added by junwei liao over 3 years ago.

Status:
New
Priority:
Normal
Assignee:
-
Category:
Performance/Resource Usage
Target version:
% Done:

0%

Source:
Community (dev)
Tags:
hash,objecter,OSD utilization ratio
Backport:
Regression:
No
Severity:
2 - major
Reviewed:
Affected Versions:
ceph-qa-suite:
Component(RADOS):
Objecter
Pull request ID:
Crash signature (v1):
Crash signature (v2):

Description

The randomness of the ceph_str_hash_rjenkins hash function causes the object to be inhomogeneous to the PG.The result is that each OSD utilization ratio is uneven.The highest utilization ratio of OSD is 10% higher than the lowest utilization ratio of OSD that causes the utilization rate of the whole cluster capacity is not high.

In addition, I use the pg-upmap command to make the same number of PG on each OSD.However, when a cluster has a OSD utilization ratio of 95%,the highest utilization ratio of OSD is still about 10% higher than the lowest utilization ratio of OSD.It can be explained that the inhomogeneity of the OSD utilization is not the crush algorithm but the inhomogeneity of the obejct to PG.


Related issues

Duplicated by RADOS - Bug #23233: The randomness of the hash function causes the object to be inhomogeneous to the PG.The result is that each OSD utilization ratio is uneven Duplicate 03/06/2018

History

#1 Updated by Nathan Cutler over 3 years ago

  • Duplicated by Bug #23233: The randomness of the hash function causes the object to be inhomogeneous to the PG.The result is that each OSD utilization ratio is uneven added

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