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Bug 1436748

Summary: LVM Cache: Be ready to consume cache metadata V2
Product: Red Hat Enterprise Linux 7 Reporter: Jonathan Earl Brassow <jbrassow>
Component: lvm2Assignee: Zdenek Kabelac <zkabelac>
lvm2 sub component: Cache Logical Volumes QA Contact: cluster-qe <cluster-qe>
Status: CLOSED ERRATA Docs Contact: Steven J. Levine <slevine>
Severity: unspecified    
Priority: unspecified CC: agk, cluster-qe, cmarthal, heinzm, heri, jbrassow, mcsontos, msnitzer, pasik, prajnoha, thornber, zkabelac
Version: 7.2Keywords: FutureFeature
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: lvm2-2.02.169-3.el7 Doc Type: Release Note
Doc Text:
LVM now supports dm-cache metadata version 2 LVM/DM cache has been significantly improved. It provides support for larger cache sizes, better adaptation to changing workloads, greatly improved startup and shutdown times, and higher performance overall. Version 2 of the dm-cache metadata format is now the default when creating cache logical volumes with LVM. Version 1 will continue to be supported for previously created LVM cache logical volumes. Upgrading to version 2 will require the removal of the old cache layer and the creation of a new cache layer.
 Story Points: ---
Clone Of: 1393566 Environment:
Last Closed: 2017-08-01 21:49:49 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1393566    
Bug Blocks:    

Description Jonathan Earl Brassow 2017-03-28 14:35:31 UTC 
+++ This bug was initially created as a clone of Bug #1393566 +++

The on-disk metadata used by dm-cache is being updated to allow for performance enhancements.  LVM will need to pass down additional DM table arguments in order to activate these changes.  We need to have a solution ready that is forward/backwards compatible.

--- Additional comment from Zdenek Kabelac on 2017-02-20 05:09:06 EST ---

So lets list the options:

lvm2 new parameter:

1.) --cacheversion   1|2|auto

2.) --cache-metadata-version 2 ?

3.) --metadata-version 2  ?

4.) --cacheformat   1|2|auto    (or maybe this: v1|v2|auto ) ?


---

libdm API options:

1.) add new dm_tree_node_set_cache_version(....) 
2.) add new dm_tree_node_set_cache_format(....) 

3.) #define DM_CACHE_FEATURE_FORMAT_2 
4.) #define DM_CACHE_FEATURE_FORMAT_V2 
5.) #define DM_CACHE_FEATURE_VERSION_2 


---

ATM I'd prefer the format to be automatically recognized by the 'cache_check' tool - as adding some 'magical' args by lvm2 to the existing configurable set can be problematic for a user - it could be done - but lvm2 will be changing passed option set.

i.e. it's then unclear if we should use:

cache_check  --metadata-version 2

and also

cache_check  --metadata-version 1

or just use it with version 2 ?

---

Waiting for more judgment here.
Comment 5 Steven J. Levine 2017-05-17 17:46:00 UTC 
Jonathan:

Should we have a release note writeup fo this feature?

Steven
Comment 6 Corey Marthaler 2017-06-22 22:08:37 UTC 
Marking this feature verified in the latest rpms.

All current cache scenarios passed with both  --cachemetadataformat 2 and 1, as well as attempted activation on older (7.3,7.2) versions. See bug 1451459 for more information on up|downgrade testing.	


3.10.0-685.el7.x86_64
lvm2-2.02.171-7.el7    BUILT: Thu Jun 22 08:35:15 CDT 2017
lvm2-libs-2.02.171-7.el7    BUILT: Thu Jun 22 08:35:15 CDT 2017
lvm2-cluster-2.02.171-7.el7    BUILT: Thu Jun 22 08:35:15 CDT 2017
device-mapper-1.02.140-7.el7    BUILT: Thu Jun 22 08:35:15 CDT 2017
device-mapper-libs-1.02.140-7.el7    BUILT: Thu Jun 22 08:35:15 CDT 2017
device-mapper-event-1.02.140-7.el7    BUILT: Thu Jun 22 08:35:15 CDT 2017
device-mapper-event-libs-1.02.140-7.el7    BUILT: Thu Jun 22 08:35:15 CDT 2017
device-mapper-persistent-data-0.7.0-0.1.rc6.el7    BUILT: Mon Mar 27 10:15:46 CDT 2017
Comment 7 errata-xmlrpc 2017-08-01 21:49:49 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2017:2222