[SERVER-18118] Question for Auto/Manual Migration Performance Created: 20/Apr/15  Updated: 21/Apr/15  Resolved: 20/Apr/15

Status: Closed
Project: Core Server
Component/s: Admin, Performance, Sharding
Affects Version/s: 2.6.6
Fix Version/s: None

Type: Question Priority: Major - P3
Reporter: Kazuo Yagi Assignee: Unassigned
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:

 Description   

Dear MongoDB Support Team,

I have a problem that automatic migration process has taken a long time to distribute chunks to new shards. It actually took 35 days in my environment until the number of all chunks became even, with the default chunk size(64M). Please see the details below for what I have done on my sharded cluster.

when what
11th, March Cluster was running with 7 shards, 2186 chunks for each.
12th, March Added new 3 shards to cluster and auto migration started. 10 shards from then on.
18th, April Migration has completed. Now, cluster is running with 10 shards, 1828 chunks for each.

My question is: would it be faster to process chunk migration if manually operated? If the manual migration will improve the speed of the entire migration process, I would opt for it when adding new shards next time.

I have had some tries at seeing how moveChunk() works with a couple of options such as `_secondaryThrottle` or `_waitForDelete` experimentally with the balancer temporarily off, however, I am not sure how it affects the whole performance.

It would be really appreciated if I could gain some of your insights about this.

Best Regards,
Kazuo Yagi



 Comments   
Comment by Ramon Fernandez Marina [ 21/Apr/15 ]

No bother at all, I reckon some times is not easy to find the right forum for each question. You may also want to take a look at https://www.mongodb.org/about/support/ for more details, and if you find a bug or have an improvement suggestion the SERVER project is definitely the right place for it.

Cheers,
Ramón.

Comment by Kazuo Yagi [ 21/Apr/15 ]

Dear Ramon,

Thank you for pointing it out. I will post this those recommended places.
I'm sorry to bother you about this.

Best Regards,
Kazuo Yagi

Comment by Ramon Fernandez Marina [ 20/Apr/15 ]

Thanks for your report ka_yagi@fancs.com. Please note that the SERVER project is for reporting bugs or feature suggestions for the MongoDB server. For MongoDB-related support discussion please post on the mongodb-user group or Stack Overflow with the mongodb tag, where your question will reach a larger audience. A question like this involving more discussion would be best posted on the mongodb-user group.

Regards,
Ramón.

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