1. Disaster Recovery
7/6/2012
© 2012 MapR Technologies Disaster Recovery 1

2. Disaster Recovery
Agenda
• Definitions & Considerations
• Disaster Preparation
• Exercise: Create a Dump File
• Exercise: Create a Remote Mirror
• Cluster Restoration
• Exercise: Restore from a Dump File
• Exercise: Copy Read-Only Data
• Final Thoughts
© 2012 MapR Technologies Disaster Recovery 2

3. Disaster Recovery
Objectives
At the end of this module you will be able to:
• Describe the important considerations involved in disaster recovery
• Identify the different approaches to disaster recovery
• Explain how to prepare for a disaster
• Create a dump file and remote mirror
• Describe the different ways of recovering from a disaster
• Restore data from a dump file
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4. Definitions &
Considerations
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5. What is Disaster Recovery?
 Disaster Recovery is a large and complex topic
– You must consider a variety of objectives and tradeoffs that involve
complex business and technical issues
– This presentation is not a tutorial on Disaster Recovery
 One key aspect of Disaster Recovery is preservation of data
– If one data center is lost, we need to ensure that there is a consistent copy
of the data available elsewhere in order to restore service
– MapR provides a solution to this problem using volume mirroring
• Data can be dumped to local storage and managed manually, or
• One cluster can replicate its data to another cluster automatically
© 2012 MapR Technologies Disaster Recovery 5

6. Considerations
 When designing your DR solution you must take into account two
key factors
– RPO – Recovery Point Objective
• Essentially this is how much data you are prepared to lose in a disaster
• This impacts how frequently you update the backup
– RTO – Recovery Time Objective
• This defines how quickly you want to restore service after a disaster
• Lower RTOs imply more automation and often pre-built backup systems
 There are two fundamental tradeoffs you must consider
– An operational cluster for recovery vs. manual rebuild
– Mirror dumps to local storage vs. automatic mirroring
© 2012 MapR Technologies Disaster Recovery 6

7. Cluster Recovery Approaches
 Your primary cluster is gone for whatever reason. You need to
restore service elsewhere
 Option #1: have an available and running cluster already prepared
– RTO will be relatively low – of course data has to be restored first
 Option #2: create a new cluster when needed
– RTO will be significantly higher
© 2012 MapR Technologies Disaster Recovery 7

8. Data Mirroring Approaches
 Option #1: dump volumes
– Dumps of course need to be moved off site
– After a disaster, obtain dumps and manually restore to cluster
• Note that if you have done incremental mirror dumps to reduce the size of the
dumps, multiple dumps will have to be restored for each volume
– Places less demand on network but
• Has high manual operational cost
• RTO is likely very high
– RPO can also involve significant data loss depending on how frequently you
move data off site
 Option #2: Mirror to a remote cluster
– Frequency of incrementals is configurable  frequency implies your RPO
– Restoration may require copying data from read only to read/write volume
– Requires operational cluster as target of mirrors
© 2012 MapR Technologies Disaster Recovery 8

9. Mirroring Key Behaviors
 Mirror data is pulled by the destination cluster
 Destination/mirror volume is read only
 Mirrors are snapshot based and thus time consistent
– Meaning that the replica mirror will have an exact copy of the data that
was present at the time of the mirror start
– There is no danger of one file being changed while the mirror is occurring
 Mirroring operation is smart enough to only replicate what has
changed since the last mirroring operation
– At the block level - changing one byte of a 1TB file triggers an 8K update,
not 1TB
 Data is compressed on the wire when transmitting
 Mirroring consumes significant network bandwidth over the WAN
– More network capacity improves rate you can mirror and thus RPO
– Plan taking into account data change rates and network bandwidth
© 2012 MapR Technologies Disaster Recovery 9

10. Disaster Preparation
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11. Preparation – no backup cluster
 Execute initial backup by dumping volume
 Move dump files to remote location
 Execute periodic dumps and move off site
 Dumps can be full or incremental
 Incremental dumps are faster but complicate restore
© 2012 MapR Technologies Disaster Recovery 11

12. Preparation – active backup cluster
 Create mirror volume on backup cluster
 Execute initial backup by dumping volume or initiate mirroring
 If the volume is large relative to network bandwidth, a
dump is likely a better choice
 Restore dump files to mirror volume if needed
 Commence remote scheduled mirroring
 If network bandwidth is scarce you can dump locally and
restore manually at other site
© 2012 MapR Technologies Disaster Recovery 12

13. Exercise:
Create a Dump File
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14. Exercise: Create a Dump File
 Full dump:
maprcli volume dump create
-name volume -dumpfile name -e statefile1
 Incremental dump
maprcli volume dump create
-s statefile1 -e statefile2
-name volume -dumpfile name
 Note: you can limit the number of incremental dumps by using different
statefiles
© 2012 MapR Technologies Disaster Recovery 14

15. Exercise:
Create a Remote Mirror
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16. Exercise: Create a Remote Mirror
 Create Mirror (on backup cluster):
maprcli volume create
-name volume_mirror -source volume@cluster –type 1
 Initiate mirroring:
maprcli volume mirror start –name volume_mirror
© 2012 MapR Technologies Disaster Recovery 16

17. Cluster Restoration
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18. Restoration

X
Build the cluster if needed
 Use offsite dumps or read only mirrors as data source
 Restore data to the cluster
 Activate cluster operations – schedule jobs, inform users,
update dependent systems, etc.
© 2012 MapR Technologies Disaster Recovery 18

19. Restoration from Dump Files
 Restore dump files to new mirror volumes
 Restore each incremental dump!
 If volumes need to be writable
 Create volumes to receive data
 Copy data from mirror volumes
© 2012 MapR Technologies Disaster Recovery 19

20. Restoration from Remote Mirrors
 Data is already there!
 If not mounted, you can just mount the mirrors
 If volumes need to be writable
 Create volumes to receive data
 Copy data from mirror volumes
© 2012 MapR Technologies Disaster Recovery 20

21. Exercise:
Restore from a Dump
File
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22. Exercise: Restore from a Dump File
 Full dump:
maprcli volume dump restore
-dumpfile name -name volume_mirror –n
 Incremental dump
maprcli volume dump restore
-dumpfile name -name volume_mirror
© 2012 MapR Technologies Disaster Recovery 22

23. Exercise:
Copy Read-Only Data
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24. Exercise: Copy Read-Only Data
 Mount mirror
maprcli volume mount –name volume_mirror -path
pathToRO
 Create Read/Write Volume:
maprcli volume create -name volume -mount 1 -path
pathToRW
 Copy data using NFS
cp –r -p /mapr/cluster/pathToRO
/mapr/cluster/pathToRW
© 2012 MapR Technologies Disaster Recovery 24

25. Final Thoughts
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26. Final Thoughts
 Active cluster with mirroring – best RPO and RTO
– Faster mirroring -> more network bandwidth but more currency (better
RPO)
– Full initial dump useful if lots of data already in primary cluster
• Sneaker net to backup cluster
– Incremental dumps with sneaker net appropriate if bandwidth constrained
 Manual dumps with offsite storage
– RPO and RTO will be worse
– Frequency of incremental dumps defines RPO
– Full vs. incremental dumps
• Full consume significantly more storage space and are slower
• Incremental will take significantly longer to restore
© 2012 MapR Technologies Disaster Recovery 26

27. Questions
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