Presentation on disaster recover for MongoDB Atlas. Different approaches to recover and restore MongoDb Data. https://elang2.github.io/myblog/

1. MongDB Backup & Disaster
Recover
Elankumaran Srinivasan

2. Why Backup & Disaster Recovery ?
Application MongoDB
Driver
Company’s Data Centre
1. Possible network issue between the data center & other external cloud services.
2. Cloud cluster down or unreachable or terminated accidentally or data deleted accidentally
Application MongoDB
Driver
Company’s Data Centre
Disaster recovery strategy is essential to quickly get access to the minimum required data and keep the
application depending on the critical data running with smallest down time.

3. Key Measurement Parameters For DR
1. Minimum time required to spin up a new cluster with snapshot data.
a) Account for snapshot data download/transfer time.
b) Cluster setup, restore and configure time.
2. Time lag between live mirrored secondary cluster and the primary cluster.
3. Can the data be restored into clusters of any topology?

4. Production Cluster On MongoDB Atlas
• Sharded Cluster.
• Two replica sets.
• Each replica set has 3 nodes. One primary and two secondary.
• 6 mongos running on the same hosts as 6 mongod.
• Config servers running as a 3 node replica set.
• Snapshots taken twice a day.
• Automatic, periodic snapshots. Useful for point in time recovery.
• Snapshots stored on Amazon S3.
• All mongos are part of a load balancer. Applications connect to these mongos through load
balancer.

5. Production Cluster On MongoDB Atlas
Shard#1 Shard#2
Instance Port
mongod 27017
mongos 37017
Primary
Secondary Secondary
mongos
mongos mongos
Load Balancer For Mongos Nodes
Application
MongoDB Driver
Mongocfg
(Primary)
Mongocfg
(Sec)
Mongocfg
(Sec)
Primary
Secondary Secondary
mongos
mongos mongos

6. Disaster Recovery (Different Approaches)
Create new cluster in
company’s data center &
restore snapshot
MongoDB Atlas
MongoDB Atlas
(Create a new cluster & restore
snapshot)
Spin up a new cluster
on AWS and restore

7. Data Restore Considerations
Different Topology
Mongo Cluster
• Restore into a sharded cluster.
• Restore into a stand alone node or a replica set.
• Restore into a cluster with similar topology as Production.
• Restore into a cluster with with a different topology.

8. Restoring Snapshot to a new Cluster on MongoDB Atlas
After selecting restore my snapshot, select the new
cluster that you provisioned on MongoDB Atlas

9. Downloading the Snapshot to restore into non-Atlas Environment

10. Steps to restore a sharded cluster ( Same Topology)
Restoring data into a new sharded cluster involves the following steps:
1. Setting up and restoring data into mongod sharded servers.
2. Setting up config servers as a replica set.
3. Setting up mongos (routers) and hooking them up to the config servers.
4. Adding sharded nodes(configured in step #1) via mongos

11. Steps to restore a sharded cluster ( Same Topology)
1. a. Set up a new cluster with the same topology as Production. Don’t start any of the mongo services.
1. b. Restore the snapshot into one of the mongod nodes. Lets assume in a path /data/db
1. c. Start the mongod on the node while pointing to the restored data path.
mongod --dbpath /data/db --replSet <replName> --shardsvr
1.d. Connect to mongo shell on the node and initiate a new replica set.
mongo
rs.initate()
Example : mongod --dbpath /data/db --replSet rs0 --shardsvr

12. Steps to restore a sharded cluster ( Same Topology)
1. e. While connected to the mongo shell , configure the replica set.
rs.initiate( { _id : "rs1", members: [ { _id : 0, host : ”s1-mongo1:27017" } ] })
1.g. Repeat steps 1.b through 1.f for replica set ”r1 ” and hosts s2-mongo1, s2-mongo2 and s2-mongo3
1. f. Add the other members of the replica set.
rs.add(”s2-mongo1”)
rs.add(”s3-mongo1”)

13. Steps to restore a sharded cluster ( Same Topology) - Contd…
2.a. Setup the 3 config servers as replica set. Start mongod as config servers for each node.
mongod --configsvr --replSet configReplSet
mongo
rs.initiate( { _id: "configReplSet", configsvr: true, members: [ { _id: 0, host:
”config01:27019" }, { _id: 1, host: ”config02:27019" }, { _id: 2, host:
”config03:27019" } ] } )
2.b. Log into one of the config server to set up the replica set and add other members to the replicaset.

14. Steps to restore a sharded cluster ( Same Topology) - Contd…
3.a. Setup 6 mongos by executing the following command on each of the mongos nodes.
mongos --configdb configReplSet/config01:27019,config02:27019,config03:27019

15. Steps to restore a sharded cluster ( Same Topology) - Contd…
4.a. Add shard#1 into the cluster. In order to do this, connect to one of the mongos shells and execute
the following command.
mongo mong01-router:27017/admin
sh.addShard( "rs0/s1-mongo1:27017,s1-mongo2:27017,s1-mongo3:27017" )
4.b. Add the nodes for shard#2 to the cluster.
sh.addShard( "rs1/s2mongo1:27017,s2-mongo2:27017,s2-mongo3:27017" )

16. Steps to restore to a single replica set.
Restoring data into a single replica set.
1. Setting up and restoring data into mongod servers. Follow the same instructions
as in Slide #10 and Slide #11 .
2. Non-Sharded cluster does not have mongos & mongod config servers.

17. Live Mirrored Stand By Cluster
Application MongoDB
Driver
Company’s Data Centre
Mongo-mirror
application
Replicate into
The Mongo connector utility can be used to migrate data from one cluster to another. This can be used to setup a live
secondary stand by cluster.
Reference : https://github.com/mongodb-labs/mongo-connector

18. Setting Up Mongo Mirror
Shard#2 Shard#2
Primary
Secondary Secondary
mongos
mongos mongos
Primary
Secondary Secondary
mongos
mongos mongos
Shard#1 Shard#2
Primary
Secondary Secondary
mongos
mongos mongos
Primary
Secondary Secondary
mongos
mongos mongos
Mongo
connector
Mongo
connector