Curious about the benefits of sharding your MongoDB deployments? Do you need help deciding when you should shard, or which collections to shard first? Or maybe you just need some guidance on finding the right shard key. This session will cover these topics and give you a primer on MongoDB sharding and why it makes the database so compelling for so many applications. This is an entry-level to medium-level talk with references and links to more advanced material on sharding MongoDB.

1. Sharding in 20 minutes
Why;Who;When;Where;
David Murphy , Mongo Master
Lead DBA, ObjectRocket
@dmurphy_data @objectrocket

2. Background
• 16 yrs in databases, development, & system
engineering
• Lead DBA @ ObjectRocket
• Mongo Master with a focus on sharding, chunks, and
scaling mongo beyond normal means.

3. What does a sharded cluster look like?

4. Why;Who;When;Where;
i) Why do we shard?
ii) Who should I shard?
iii) When do we shard?
iv) Where is my shard key

5. Why do we shard?
• Scaling out write locks

6. Why do we shard?
• Scaling out write locks
• Small dataset to search per node

7. Why do we shard?
• Scaling out write locks
• Small dataset to search per node
• Getting more connections to the data

8. Why do we shard?
• Scaling out write locks
• Small dataset to search per node
• Getting more connections to the data
• More smaller node vs Scaling up to expensive
nodes

9. Who should I shard?
• Biggest Collections by Size

10. Who should I shard?
• Biggest Collections by Size
• Busiest Collection by changes

11. Who should I shard?
• Biggest Collections by Size
• Busiest Collection by changes
• Groupings of data (example):
• State/Country
• UserID
• Company
• Category

12. When do I shard?
ALWAYS as early as possible!

13. When do I shard?
ALWAYS as early as possible!
Reasons:
• Not all commands work

14. When do I shard?
ALWAYS as early as possible!
Reasons:
• Not all commands work
• Future Proof - No recoding

15. When do I shard?
ALWAYS as early as possible!
Reasons:
• Not all commands work
• Future Proof - No recoding
• Adding index once your live can take time
you don’t have!

16. Where (and what) is my shard key?
You have to pick your own :/
But there are some quick hints…

17. Where (and what) is my shard key?
Sharding Quick Hints:
• Hashed Shard keys
Great for even disk usage
Uses Scatter-Gathers == More Conns
Dates,Increasing IDs , and text are great here

18. Where (and what) is my shard key?
Sharding Quick Hints:
• Hashed Shard keys
Great for even disk usage
Uses Scatter-Gathers == More Conns
Dates,Increasing IDs , and text are great here
• Non-Hashed Keys
Use profiler_level:2 & review ALL operations
Things you wont change only
No Dates
No Increasing ID numbers
No Text

19. Why mongo sharding/balancing
Modulus Sharding with MySQL:
Hard to rebalance online
Requires application coding to support
Ring Topologies like Cassandra -
Cant change schema online
Hard to rebalance online

20. Further Reading
Presentations:
Kenny Gorman Sharding - bit.ly/1oXYDfm
David Murphy - Adv Sharding for Operations - bit.ly/1oXYDfm
Other Sharding MongoDB Links - bit.ly/ZTtDI1
Picking a shard key (manual) - http://bit.ly/1ozuzMH
Choosing a shard key - http://slidesha.re/1nBnGtq

21. Contact
@dmurphy_data
@objectrocket
david@objectrocket.com
https://www.objectrocket.com
WE ARE HIRING! (DBA,DEVOPS, and more)
https://www.objectrocket.com/careers