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80a disaster recovery
- 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
© 2012 MapR Technologies Disaster Recovery 3
- 4. Definitions &
Considerations
© 2012 MapR Technologies Disaster Recovery 4
- 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
- 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
© 2012 MapR Technologies Disaster Recovery 13
- 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
© 2012 MapR Technologies Disaster Recovery 15
- 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
- 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
© 2012 MapR Technologies Disaster Recovery 21
- 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
© 2012 MapR Technologies Disaster Recovery 23
- 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
- 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
Hinweis der Redaktion
- KDB: This information really belongs in the earlier deck on volumes in the mirroring section, but the information is not there, so I put it here.