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SQL Server Disaster Recovery. Chris Shaw Sr. SQL Server DBA, Xtivia Inc. Christopher Shaw. Microsoft SQL Server MVP [email protected] Twitter @ SQLShaw http ://chrisshaw.wordpress.com/ SQL PASS Regional Mentor Contributing Author for 3 SQL Server Books (working on 4 th ) - PowerPoint PPT Presentation
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SQL Server Disaster Recovery
Chris ShawSr. SQL Server DBA, Xtivia Inc.
Christopher Shaw
Microsoft SQL Server MVP [email protected] Twitter @SQLShaw http://chrisshaw.wordpress.com/
SQL PASS Regional Mentor Contributing Author for 3 SQL Server
Books (working on 4th) A full time VDBA
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Success Requires Planning Start planning now. Document your plan, and update regularly.
Create hard copies and soft copies of your
plan, keep a copy of your plan with your backups.
Predetermine layers of recovery.
Tip – Have increased understanding of your business and goals as a whole and not just the task goal. Maximize resource usage.
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Define “Disaster”
Tip – Your company servers don’t know the difference between a fire, a flood or a bad disk drive. A crash is a just a crash. Down is simply down.
Anything impacting the availability of your data.
Human Error Storage Failure Power Failure Memory Failure Natural disasters The cable guy down the street
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Define “Disaster”
Tip – Your company servers don’t know the difference between a fire, a flood or a bad disk drive. A crash is a just a crash.
Your company is much more likely to experience a hardware issue than a natural disaster.
76% of effected businesses have not been impacted by a natural disaster.
Most common cause of system failures is HARDWARE. Annual disk replacements have been documented as high
as 13%. Inside attacks and user error account for the majority of
business downtime. 70% of all successful attacks on networks were carried out
by employees and insiders. Disaster “downtime” can co$t your company Companies lose an average of $84,000 for each hour of
downtime.
Do you remember this?
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The Two Design Questions
Define the Goal – What is: RTO – Recovery Time Objective.
- The Amount of acceptable downtime RPO – Recovery Point Objective.
- The Amount of maximum data loss.
Tip –This is planning for worst case scenario. No one wants to say they can be down for extended periods of time, or lose any data. Yet over aggressive goals can increase the cost of your solution.
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The Keys to Success
Identify the Resources Define the Budget Evaluate costs of downtime to cost of high
availability. What is it worth? Compliance Requirements (HIPA, SOX, SSAE 16 etc.)
Tip –This is planning for worst case scenario. No one wants to say they can be down for extended periods of time, or lose any data. Yet over aggressive goals can increase the cost of your solution.
Outage Types Site Outage
Hardware Outage
Database Outage
Site Outage
Hardware Outage
Database Outage
Possible Site Outages
Technology Options Transaction Log Shipping Mirror AlwaysOn
Potential Examples: Natural disaster, Fire, Flood, Global emergency, Power Outages.
Effect all levels
Site Outage
Hardware Outage
Database Outage
Possible Hardware Outages
Technology Options Redundant Hardware RAID Windows Clustering Transaction Log Shipping Geo – Cluster Mirror AlwaysOn
Potential Examples: Storage issue, bad drive, memory crash, power supply
SiteOutage
Hardware Outage
Database Outage
Possible Database Outages
Technology Options Backup / Restore Transaction Log Backups Database Snapshots Snapshot Replication Snapshots Transaction Log Shipping Geo – Cluster Mirror AlwaysOn
Potential Examples: Human error, bug, bad release
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Automated failover
Fail back
Latency
Secondary Readable
Multiple Secondary
Outside objects
Potential Data Loss
Failover Time
Cost
Transaction Log Shipping
Database
Backups
True
Require Configuration
Based on Backups
Slow
Inexpensive
False
False
Based on Backups
Yes, with restrictions
Tip – Great inexpensive way to have a DR copy and a reporting server. However requires a lot of added configuration, and failback requires reconfiguration.
Transactional Replication
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Automated failover
Fail back
Latency
Secondary Readable
Multiple Secondary
Outside objects
Potential Data Loss
Failover Time
Cost
True
Require Configuration
Based on Configuration
Slow
Inexpensive
False
False
Based on Agents
Yes
Database
Copy Distributor
Clusters Two or more servers that act as one
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Automated failover
Fail back
Latency
Secondary Readable
Multiple Secondary
Outside objects
Potential Data Loss
Failover Time
Cost
False
Move with database
Small
Fast ( 5 seconds +)
Expensive
True
True
None
No
Tip – Does a great job of protecting you from hardware issues. However if the storage fails your database will go down.
Mirroring Similar to Replication
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Automated failover
Fail back
Latency
Secondary Readable
Multiple Secondary
Outside objects
Potential Data Loss
Failover Time
Cost
False
Requires Manual Configuration
Small
Fast (Dependent on connection)
Varies on Configuration
Varies on Configuration
True
Varies on Configuration
No
Database
Database
Witness
Tip – Great option for companies that don’t run standard edition.
AlwaysOn Availability Groups
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Automated failover
Fail back
Latency
Secondary Readable
Multiple Secondary
Outside objects
Potential Data Loss
Failover Time
Cost
True
Partial
Small
Fast (Dependent on connection)
Most Expensive
Varies on Configuration
True
Varies on Configuration
Yes
Database
Database
Database
Tip – Ideal for companies that want to make use of all the resources they have however the cost is larger than other solutions
DR Options Matrix
1 - Objects required outside of database need to be preconfigured2 - Consider the failover to be one way. To go back to original hardware reconfig and failover required3 - Not 100% some items may need to be pre-configured 4 – Common misconception5 – Feature is going to be removed from SQL Server in future editions to be replaced by AlwaysOn
There is no single cookie cutter solution that will fit every companies needs.
Technology changes, offering new solutions with each release.
Businesses grow, and requirements change. Building without testing and updating is similar to not
doing anything at all. The shorter the latency the greater likelihood to
propagate corruption. Increased latency increases data loss potential
Past Experience
Thank You for Your Time…
Questions?
