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Achieving Zero Downtime for SQL
©2017 ScaleArc. All Rights Reserved. 2
Downtime is disruptive and costly
• Poor user experience• Decreased productivity• Wasted time and IT resources• Lost revenue
©2017 ScaleArc. All Rights Reserved. 3
Two Sources of Downtime
• Unplanned Outages– A strong failover architecture is imperative
– Instantly identify and automatically reroute traffic away from a failed database server, even across data centers
– Avoid application errors and user dissatisfaction
• Planned Maintenance– Carefully examine your database maintenance strategy
• Are you bringing servers completely offline for maintenance?
• Are you disabling applications associated with those databases during maintenance?
©2017 ScaleArc. All Rights Reserved. 4
Want Guaranteed Downtime?
Keep your applications directly connected to your databases
This 1:1 tie will guarantee that any database hiccup will make your application
throw up
Or…
©2017 ScaleArc. All Rights Reserved. 5
Leverage the Fact that Databases are Getting Smarter
Modern databases offer:• Scale out• Better replication• Automatic failover
But make one key change:End the 1:1 tie between apps and databases by inserting an
abstraction layer.
©2017 ScaleArc. All Rights Reserved. 6
An Abstraction Layer is Critical for Zero Downtime
• Database Load Balancing Software acts as a buffer
PrimaryPrimary SecondaryPrimary
replicationSecondary
• Leverages database replication and failover
• Makes failover invisible to the app by queing writes until the new primary is ready
• Enables servers to go offline for maintenance without taking down the app
Database Load Balancing Software
©2017 ScaleArc. All Rights Reserved. 7
ScaleArc’s Database Load Balancing Software
• Intelligently directs traffic into the database on behalf of the app• Deploys transparently, with no changes to app or database• Leverages and augments database’s replication and failover
©2017 ScaleArc. All Rights Reserved. 8
Avoid Downtime during Unplanned Outages
PrimaryPrimary SecondaryPrimary
replicationSecondary
©2017 ScaleArc. All Rights Reserved. 9
PrimaryPrimary SecondaryPrimary
replication
Avoid Downtime during Unplanned Outages
Secondary
1 ScaleArc performs read/write split
©2017 ScaleArc. All Rights Reserved. 10
PrimaryPrimary SecondaryPrimary
replication
Avoid Downtime during Unplanned Outages
Secondary
1 ScaleArc performs read/write split
RRR
WR W R R
W
©2017 ScaleArc. All Rights Reserved. 11
Primary Secondary
replication
Avoid Downtime during Unplanned Outages
Secondary
1 ScaleArc performs read/write split
R
WR W R R
W2 Upon database failure,
ScaleArc queues writesW
W
©2017 ScaleArc. All Rights Reserved. 12
Primary Secondary
replication
Avoid Downtime during Unplanned Outages
Secondary
1 ScaleArc performs read/write split
R
WR W R R
2 Upon database failure, ScaleArc queues writes
3 After secondary is promoted, ScaleArc directs queries to new primary server
Primary
WWW
©2017 ScaleArc. All Rights Reserved. 13
Primary Secondary
replication
Avoid Downtime during Unplanned Outages
Secondary
1 ScaleArc performs read/write split
R
WR W R R
2 Upon database failure, ScaleArc queues writes
3 After secondary is promoted, ScaleArc directs queries to new primary server
Primary
WWW
4 Apps see delay, but do not restart
©2017 ScaleArc. All Rights Reserved. 14
SecondarySecondary
replication
Enable Zero Downtime Maintenance
SecondaryPrimary
WRRWR
RW
WR R
©2017 ScaleArc. All Rights Reserved. 15
Secondary
replication
Enable Zero Downtime Maintenance
Secondary
1 Mark a database to be taken offline
Primary
WRRWR
RW
WR R
©2017 ScaleArc. All Rights Reserved. 16
Secondary
replication
Enable Zero Downtime Maintenance
Secondary
1 Mark a database to be taken offline
Primary
WRRWR
RW
WR
2 ScaleArc automatically reroutes queries away from offline server
©2017 ScaleArc. All Rights Reserved. 17
Secondary
replication
Enable Zero Downtime Maintenance
Secondary
1 Mark a database to be taken offline
Primary
WRRWR
RW
WR
2 ScaleArc automatically reroutes queries away from offline server
3 Patch the server and bring it back online
©2017 ScaleArc. All Rights Reserved. 18
SecondarySecondary
replication
Enable Zero Downtime Maintenance
SecondaryPrimary
WRRWR
RW
WR R
4 After health check, ScaleArc auto restores traffic to updated server
3 Patch the server and bring it back online
2 ScaleArc automatically reroutes queries away from offline server
1 Mark a database to be taken offline
©2017 ScaleArc. All Rights Reserved. 19
ScaleArc Keeps Business Data Flowing
• Avoid lost productivity and business profitability• Ensure customer satisfaction• Keep critical data flowing
©2017 ScaleArc. All Rights Reserved. 20
Achieving Zero Downtime for SQL
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