Project

General

Profile

Bug #52886

osd: backfill reservation does not take compression into account

Added by Mykola Golub over 2 years ago. Updated over 2 years ago.

Status:
New
Priority:
Normal
Assignee:
-
Category:
-
Target version:
-
% Done:

0%

Source:
Tags:
Backport:
Regression:
No
Severity:
3 - minor
Reviewed:
Affected Versions:
ceph-qa-suite:
Component(RADOS):
Pull request ID:
Crash signature (v1):
Crash signature (v2):

Description

The problem may be observed with the recently added backfill-toofull test when it runs with bluestore-comp-lz4. When calculating the expected backfillfull ratio the test uses compressed data, i.e. what is actually stored on the disk, while the osd reservation check uses uncompressed data statistics.

Although the test may be updated to pass this scenario, the osd behavior may be not correct in this case. Consider a case when compression is enabled and data has high compression ratio (> 2). In this case we may face a situation when backfill will be "backfillfull" rejected while the osd will still have more than a half of the space available.

[1] https://pulpito.ceph.com/trociny-2021-10-08_15:57:02-rados-master-distro-basic-smithi/

History

#1 Updated by Neha Ojha over 2 years ago

I'll create a trello card to track this, I think the initial toofull implementation was intentionally kept simple, but it is time to improve it further.

#2 Updated by Neha Ojha over 2 years ago

Neha Ojha wrote:

I'll create a trello card to track this, I think the initial toofull implementation was intentionally kept simple, but it is time to improve it further.

https://trello.com/c/mbLAnFLY/767-backfill-reservation-should-take-compression-into-account

Also available in: Atom PDF