[Bugs] [Bug 1333224] New: read/write performance degrades as the cache tier fills up
bugzilla at redhat.com
bugzilla at redhat.com
Thu May 5 01:48:28 UTC 2016
https://bugzilla.redhat.com/show_bug.cgi?id=1333224
Bug ID: 1333224
Summary: read/write performance degrades as the cache tier
fills up
Product: GlusterFS
Version: 3.7.10
Component: tiering
Severity: low
Priority: medium
Assignee: bugs at gluster.org
Reporter: pcuzner at redhat.com
QA Contact: bugs at gluster.org
CC: bugs at gluster.org
Description of problem:
During a continuous write workload, writes were accelerated by the cache layer
up until the low watermark was reached. At this point performance to the client
degraded to pre-cache levels.
Version-Release number of selected component (if applicable):
How reproducible:
Tried several times, and each time the effect was observed
Steps to Reproduce:
1. create a tier volume with SSD as the tier
2. create files on the volume with dd repeatedly
3. observe throughput degradation as the tier > 60% utilised
Actual results:
client writes degrade considerably
Expected results:
client writes should degrade, but I saw 150MB/s become 4MB/s
Additional info:
The test environment I used was vm's under KVM. Each gluster node has an SSD
disk for hot, and a replica 2 for cold tier.
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