[SERVER-13106] about an uneven chunk distribution Created: 08/Mar/14  Updated: 18/Mar/14  Resolved: 18/Mar/14

Status: Closed
Project: Core Server
Component/s: Sharding
Affects Version/s: 2.2.2
Fix Version/s: None

Type: Question Priority: Minor - P4
Reporter: liao Assignee: Stennie Steneker (Inactive)
Resolution: Incomplete Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:

 Description   

Shard001 chunks is 1000 large than other‘s shard;
How I slove it? this msg :

                logsystem.logs chunks:
                                shard002        2762
                                shard000        2761
                                shard003        2768
                                shard004        2764
                                shard001        3712

hope your answer ,thx!!!



 Comments   
Comment by Stennie Steneker (Inactive) [ 18/Mar/14 ]

Hi Liao,

As Scott noted the appropriate forum for this sort of support question is the mongodb-user discussion group.

Some common reasons for a chunk imbalance include:

  • the sharded cluster balancer is turned off and you have chosen a monotonically increasing shard key (such as an ObjectID) which causes all inserts to go to the same shard
  • your shard key has poor cardinality, leading to creation of "jumbo chunks" that cannot be further divided (and will not be migrated)
  • you have set some values such as tag aware sharding or maxSize which can affect the chunk distribution

It's impossible to know what the cause might be in your specific case without further information. If you are still interested in investigating, I would suggest starting a discussion on the mongodb-user group with extra details including:

  • description of the shard key for your collection
  • whether the balancer is enabled
  • updated count of chunks (to see if the distribution is changing over time)

Thanks,
Stephen

Comment by Scott Hernandez (Inactive) [ 08/Mar/14 ]

Can you please attach the logs from your mongos server which is acting as the balancer and a mongodump of your config database? If you are unsure which node is the balancer then just attach the config db mongodump and we can look to see which logs we would need.

Also, these questions are best asked on the community mongodb-users (https://groups.google.com/group/mongodb-user) where questions like may already have answers. This jira project is primarily for filing issues for bugs, features and the like.

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