Bug 1464739 - Cache & thin pool target always commits data even for unused devices
Cache & thin pool target always commits data even for unused devices
Status: NEW
Product: LVM and device-mapper
Classification: Community
Component: device-mapper (Show other bugs)
Unspecified Unspecified
unspecified Severity unspecified
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Assigned To: Joe Thornber
Depends On:
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Reported: 2017-06-25 05:39 EDT by Zdenek Kabelac
Modified: 2017-06-25 05:41 EDT (History)
6 users (show)

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rule-engine: lvm‑technical‑solution?

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Description Zdenek Kabelac 2017-06-25 05:39:53 EDT
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):

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:

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