[SERVER-76405] Reduce the initial minimum number of chunks to 1 per shard for empty collections with hashed shard key Created: 21/Apr/23  Updated: 29/Oct/23  Resolved: 17/Oct/23

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: 7.2.0-rc0

Type: Improvement Priority: Major - P3
Reporter: Pierlauro Sciarelli Assignee: Robert Sander
Resolution: Fixed Votes: 0
Labels: sharding-wfbf-day
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Documented
is documented by DOCS-16446 Investigate changes in SERVER-76405: ... Closed
Related
is related to SERVER-82068 Investigate handling of MinKey and Ma... Open
is related to SERVER-81884 Get rid of featureFlagOneChunkPerShar... Open
is related to SERVER-82216 Make a more even distribution of chun... Backlog
is related to SERVER-74747 Deprecate `numInitialChunks` paramete... Closed
Assigned Teams:
Sharding EMEA
Backwards Compatibility: Fully Compatible
Sprint: Sharding EMEA 2023-07-24, Sharding EMEA 2023-08-07, Sharding EMEA 2023-10-02, Sharding EMEA 2023-10-16, Sharding EMEA 2023-10-30
Participants:

 Description   

Following the removal of the auto-splitter in versions >= v6.0.3, balancing does not happen anymore on number of chunks but on actual data size and the balancer is issuing moveRange commands (DOCS-15363) to atomically split+move subparts of a chunk.

Purpose of this ticket is to change the default behavior for creating/distributing chunks when sharding an empty collection with hashed shard key: one chunk per shard, in line with the decision taken also for resharding (SERVER-68050).



 Comments   
Comment by Robert Sander [ 18/Oct/23 ]

Added the downstream impact on Docs. Thanks!

Comment by Githook User [ 17/Oct/23 ]

Author:

{'name': 'Robert Sander', 'email': 'robert.sander@mongodb.com', 'username': 'robsndr'}

Message: SERVER-76405 Reduce the initial minimum number of chunks to 1 per shard for empty collections with hashed shard key
Branch: master
https://github.com/mongodb/mongo/commit/3c62f258d138d80f506e4fa4af15893622ab2884

Comment by Pierlauro Sciarelli [ 27/Apr/23 ]

Is the change going from 2 chunks per shard to just one?

Correct. Not a big deal, only for not getting users confused on the usefulness of having more chunks.

Comment by Sergi Mateo Bellido [ 27/Apr/23 ]

pierlauro.sciarelli@mongodb.com : Is the change going from 2 chunks per shard to just one?

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