Bug 1464739

Summary:	Cache & thin pool target always commits data even for unused devices
Product:	[Community] LVM and device-mapper	Reporter:	Zdenek Kabelac <zkabelac>
Component:	device-mapper	Assignee:	Joe Thornber <thornber>
Status:	NEW ---	QA Contact:	cluster-qe <cluster-qe>
Severity:	unspecified	Docs Contact:
Priority:	low
Version:	2.02.172	CC:	agk, heinzm, jbrassow, msnitzer, prajnoha, zkabelac
Target Milestone:	---	Keywords:	Triaged
Target Release:	---	Flags:	rule-engine: lvm-technical-solution?
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OS:	Unspecified
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Description Zdenek Kabelac 2017-06-25 09:39:53 UTC

Description of problem:

When user creates thin-pool with unused  thin LV, or  caches a volume, then every call a flushing  'dmsetup status' cause  very small i/o batch to pass on actual real device.

This is not a big deal in case performance, but it prevents unused 'devices' to stay in sleep eventually wakes them up whenever admin runs: 

dmsetup status.

As a workaround to keep disks sleeping - user may 'add --noflush' arg...



Version-Release number of selected component (if applicable):
4.12.0-0.rc6.git3.2.fc27.x86_64

How reproducible:


Steps to Reproduce:
1. create  thinLV  (lvcreate -L10 -V10 -T vg/pool -n thinLV)  (or cache some LV)
2. iostat -d 1
3. observe i/o load with every 'dmsetup status' call

Actual results:


Expected results:


Additional info: