Bug 2222951

Summary:	RFE: support conversion of LV to thin LV by setting original LV as thin-pool data
Product:	Red Hat Enterprise Linux 9	Reporter:	Zdenek Kabelac <zkabelac>
Component:	lvm2	Assignee:	Zdenek Kabelac <zkabelac>
lvm2 sub component:	Thin Provisioning	QA Contact:	cluster-qe <cluster-qe>
Status:	NEW ---	Docs Contact:
Severity:	medium
Priority:	unspecified	CC:	agk, heinzm, jbrassow, msnitzer, prajnoha, thornber, zkabelac
Version:	9.4	Keywords:	FutureFeature, Triaged
Target Milestone:	rc
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Description Zdenek Kabelac 2023-07-14 15:10:02 UTC

Description of problem:

Users with existing data in i.e. Linear, Raid, VDO LVs may need to use then with thin-provisioning. While lvm2 already supports such user through 'external' origin, there could be cases where a direct conversion to thin-pool is better solutions.

To support this extend the 'lvconvert' with new supported conversion, that makes the original volume basically a 'data' volume for thin-pool and adds a thin volume with fully provisioned  volume mapping this data.

Such conversion should be possible to happen 'online' so user should not need to deactivate such LV.


Expected usage:

lvcreate -L10 -n normalLV  vgname

lvconvert --type thin  vgname/normalLV


Results with thin-pool with normalLV   being represented by thin.

Comment 2 Zdenek Kabelac 2023-07-14 15:12:22 UTC

Upstream code already provides the initial support with some limitation.

Currently user has to manually 'extend' thin-pool if he want to use thin-pool for creation of futher thin LVs in the same pool.

Comment 4 Zdenek Kabelac 2023-07-14 15:15:58 UTC

Also the primary use-case for this conversion can be seen by allowing to create multiple LVs within the single VDOPOOL.

User can convert 'VDOLV' into a thin volume with thin-pool having back-end in compressed deduplicated data volume handled by VDO target.