Bug 1639833

Summary: [RFE] Enabling CRUSH device classes should not incur data movement in the cluster
Product: [Red Hat Storage] Red Hat Ceph Storage Reporter: Mike Hackett <mhackett>
Component: RADOSAssignee: Josh Durgin <jdurgin>
Status: CLOSED ERRATA QA Contact: Manohar Murthy <mmurthy>
Severity: high Docs Contact:
Priority: high    
Version: 3.1CC: aguetta, anharris, ceph-eng-bugs, dzafman, edonnell, jdurgin, kchai, kjosy, nojha, pasik, sweil, tchandra, tserlin, vumrao
Target Milestone: z2Keywords: FutureFeature
Target Release: 3.2   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: RHEL: ceph-12.2.8-113.el7cp Ubuntu: ceph_12.2.8-96redhat1xenial Doc Type: Enhancement
Doc Text:
.Upgrading to the latest version no longer causes cluster data movement Previously, upgrading a {product} cluster to the latest version when CRUSH device classes were enabled, the `crushtool` utility rebalanced data in the cluster because of changes in the CRUSH map. This data movement should not have occurred. With this update, a reclassify functionality is available to help transition from older CRUSH maps that maintains parallel hierarchies for OSDs of different types to a modern CRUSHmap that makes use of the device class feature without triggering data movement.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2019-04-30 15:56:43 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:    
Bug Blocks: 1629656    
Attachments:
Description Flags
updated crush map none

Description Mike Hackett 2018-10-16 17:30:13 UTC 
Description of problem:
Currently when a legacy cluster is upgraded to Luminous (RHCS 3.y) and CRUSH device classes are enabled CRUSH will rebalance data in the cluster due to a change in the CRUSH map.
Reclassifying devices should not incur a data movement as we are only applying a label.

Upstream PR: 
https://github.com/ceph/ceph/pull/24502

Version-Release number of selected component (if applicable):
3.y
Comment 4 Sage Weil 2018-10-17 16:19:30 UTC 
I am finalizing a tool to handle this in https://github.com/ceph/ceph/pull/24502
Comment 5 Josh Durgin 2018-10-17 21:37:14 UTC 
*** Bug 1638228 has been marked as a duplicate of this bug. ***
Comment 13 Sage Weil 2018-10-23 19:27:40 UTC 
Created attachment 1496814 [details]
updated crush  map

Updated CRUSH map that uses hdd-sas and hdd-sata classes.  All mappings should be identical to before (no PGs should move).
Comment 26 errata-xmlrpc 2019-04-30 15:56:43 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/RHSA-2019:0911