Bug #14397
disable filestore_xfs_extsize by default
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Description
Description of problem:
filestore_xfs_extsize defaults to "true" in Hammer. This option is designed to reduce fragmentation on the OSDs.
Tests have found that disabling filestore_xfs_extsize in Hammer improves large sequential write performance by about 20% (Ben Turner's cluster), and in some other tests by lesser amounts. This brings us closer to the large sequential write performance of Firefly.
Steps to Reproduce:- Leave filestore_xfs_extsize unset (currently defaults to "true"),
- Run large sequential writes tests via CBT, note performance numbers,
- Set filestore_xfs_extsize to "false",
- Re-run large sequential writes in CBT, note performance numbers.
Actual results:
The default filestore_xfs_extsize setting results in a large sequential write performance degradation.
Expected results:
The default filestore_xfs_extsize setting should not result in a large sequential write performance degradation.
The proposed fix is to set filestore_xfs_extsize back to "false" in src/common/config_opts.h
.
Additional info:
This change comes with a trade-off, because it introduces fragmentation on the OSDs. To address this, we should introduce documentation which explains the fragmentation cost and suggest that users who have a large sequential read use-cases (object storage/CDN) toggle the value to reduce the fragmentation impact over time.
Related issues
Associated revisions
osd: disable filestore_xfs_extsize by default
This option involves a tradeoff: When disabled, fragmentation is worse,
but large sequential writes are faster. When enabled, large sequential
writes are slower, but fragmentation is reduced.
Fixes: #14397
osd: disable filestore_xfs_extsize by default
This option involves a tradeoff: When disabled, fragmentation is worse,
but large sequential writes are faster. When enabled, large sequential
writes are slower, but fragmentation is reduced.
Fixes: #14397
(cherry picked from commit aed85775bf53c273786ce4999320134822722af5)
History
#1 Updated by Ken Dreyer about 8 years ago
- Backport set to hammer
#2 Updated by Ken Dreyer about 8 years ago
- Status changed from New to Fix Under Review
PR for master: https://github.com/ceph/ceph/pull/7265
#3 Updated by Sage Weil about 8 years ago
- Status changed from Fix Under Review to Pending Backport
#4 Updated by Loïc Dachary about 8 years ago
- Copied to Backport #14467: hammer: disable filestore_xfs_extsize by default added
#5 Updated by Nathan Cutler about 8 years ago
- Status changed from Pending Backport to Resolved