Solution Architect, MongoDB

chad.tindel@mongodb.com

@ctindel

Chad Tindel

#MongoDBWorld

Hardware Provisioning

MongoDB is so easy for programmers….

Even a baby can write an application!

MongoDB is so easy to manage with MMS…

Even a baby can manage a cluster!

Hardware Selection for MongoDB is….

Not so easy!

Text Over Photo

A Cautionary Tale

The methodology (in theory)

Requirements – Step One

• It is impossible to properly size a MongoDB cluster without first documenting your business requirements

• Availability: what is your uptime requirement?

• Throughput

• Responsiveness– what is acceptable latency?– is higher latency during peak times acceptable?

Requirements – Step Two

• Understand your own resources available to you– Storage– Memory– Network– CPU

• Many customers limited to the options available in AWS or presented by their own Enterprise Virtualization team

Continuing Requirements – Step Three• Once you deploy initially, it is common for

requirements to change– More users added to the application

• Causes more queries and a larger working set– New functionality changes queries patterns

• New indexes added causes a larger working set– What started as a read-intensive application can add more

and more write-heavy workloads• More write-locking increases reader queue depth

• You must monitor and collect metrics and update your hardware selection as necessary (scale up / Add RAM? Add more shards?)

Run a Proof of Concept

• Forces you to:– Do schema / index design– Understand query patterns– Get a handle on Working Set size

• Start small on a single node– See how much performance you can get from one box

• Add replication, then add sharding– Understand how these affect performance in your use

case

• POC can be done on a smaller scale to infer what will be needed for production

POC – Requirements to Gather

Data Sizes– Total Number of Documents– Average Document Size– Size of Data on Disk– Size of Indexes on Disk– Expected growth– What is your document model?

• Ingestion– Insertions / Updates / Deletes per second, peak &

average– Bulk inserts / updates? If so, how large and how often?

POC – Requirements to Gather

• Query Patterns and Performance Expectations– Read Response SLA– Write Response SLA– Range queries or single document queries?– Sort conditions– Is more recent data queried more frequently?

• Data Policies– How long will you keep the data for?– Replication Requirements– Backup Requirements / Time to Recovery

POC – Requirements to Gather

• Multi-datacenter Requirements– Number and location of datacenters– Cross DC latency– Active / Active or Active / Passive?– Geographical / Data locality requirements?

• Security Requirements– Encryption over the wire (SSL) ?– Encryption of data at rest?

Resource Usage

• Storage– IOPS– Size– Data & Loading

Patterns

• Memory

– Working Set

• CPU– Speed– Cores

• Network– Latency– Throughput

Storage Capability

7,200 rpm SATA ~ 75-100 IOPS

15,000 rpm SAS ~ 175-210 IOPS

Amazon SSD EBS ~ 4000 PIOPS / Volume~ 48,000 PIOPS / Instance

Intel X25-E (SLC) ~ 5,000 IOPS

Fusion IO ~ 135,000 IOPS

Violin Memory 6000 ~ 1,000,000 IOPS

Storage Measuring

Storage Measuring

Memory Measuring

• Added in 2.4– workingSet option on db.serverStatus() > db.serverStatus( { workingSet: 1 } )

Network

• Latency– WriteConcern– ReadPreference

• Throughput– Update/Write Patterns– Reads/Queries

• Come to love netperf

CPU Usage

• Non-indexed Queries

• Sorting

• Aggregation– Map/Reduce– Framework

Case Studies (theory applied)

Case Study #1: A Spanish Bank

• Problem statement: want to store 6 months worth of logs

• 18TB of total data (3 TB/month)

• Primarily analyzing the last month’s worth of logs, so Working Set Size is 1 month’s worth of data (3TB) plus indexes (1TB) = 4 TB Working Set

Case Study #1: Hardware Selection

• QA Environment– Did not want to mirror a full production cluster. Just

wanted to hold 2TB of data– 3 nodes / shard * 4 shards = 12 physical machines– 2 mongos – 3 config servers (virtual machines)

• Production Environment– 3 nodes / shard * 36 shards = 108 physical machines– 128GB/RAM * 36 = 4.6 TB RAM– 2 mongos – 3 config servers (virtual machines)

Case Study #2: A Large Online Retailer• Problem statement: Moving their product

catalog from SQL Server to MongoDB as part of a larger architectural overhaul to Open Source Software

• 2 main datacenters running active/active• On Cyber Monday they peaked at 214

requests/sec, so let’s budget for 400 requests/sec to give some headroom

Case Study #2: The POC

• A POC yielded the following numbers:– 4 million product SKUs, average JSON document

size 30KB• Need to service requests for:

– a specific product (by _id)– Products in a specific category (i.e. “Desks” or

“Hard Drives”)• Returns 72 documents, or 200 if it’s a

google bot crawling)

Case Study #2: The Math

• Want to partition (Shard) by category, and have products that exist in multiple categories duplicated– The average product appears in 2 categories, so we

actually need to store 8M SKU documents, not 4M

• 8M docs * 30KB/doc = 240GB of data

• 270 GB with indexes

• Working Set is 100% of all data + indexes as this is a core functionality that must be fast at all times

Case Study #2: Our Recommendation

• MongoDB initial recommendation was to deploy a single Replica Set with enough RAM in each server to hold all the data (at least 384GB RAM/server)

• 4 node Replica Set (2 nodes in each DC, 1 arbiter in a 3rd DC)– Allows for a node in each DC to go down for maintenance or

system crash while still servicing the application centers in that datacenter

• Deploy using secondary reads (NEAREST read preference)

• This avoids the complexity of sharding, setting up mongos, config servers, worrying about orphaned documents, etc.

Node 1Primary

Node 2Secondary

Node 3Secondary

Node 3Secondary

Datacenter 3

Arbiter

Datacenter 1 Datacenter 2

Case Study #2: Actual Provisioning

• Customer decided to deploy on their corporate VMWare Cloud

• IT would not give them nodes any bigger than 64 GB RAM

• Decided to deploy 3 shards (4 nodes each + arbiter) = 192 GB/RAM cluster wide into a staging environment and add a fourth shard if staging proves it would be worthwhile

Key Takeaways

• Document your performance requirements up front

• Conduct a Proof of Concept• Always test with a real workload• Constantly monitor and adjust based on

changing requirements

Solution Architect, MongoDB

Chad Tindel

#MongoDBWorld

Thank You