High Availability Options for Modern Oracle Infrastructures

High Availability Options for
Modern Oracle Infrastructures

Simon Haslam Julian Dyke
Veriton Limited juliandyke.com

1 (1.2h) ©2011 Veriton Limited juliandyke.com

Simon Haslam / Veriton
Specialised consultant & Oracle Partner,
established for 15 years

Oracle Fusion Middleware
(Java EE, SSO, OAM, OID, clustering)
ADF Applications (esp. strategy & admin)

Database & related technologies
(Solaris/Linux, load balancers, firewalls, …)


Julian Dyke / juliandyke.com

Independent database consultant specialising in
Oracle performance tuning and HA, including
RAC and Data Guard


Agenda
1. High Availability Outline
2. Generic HA
3. Database HA
4. Middleware HA
5. Summary

High Availability Definition
Wikipedia:
“ High availability is a system design approach
and associated service implementation that
ensures a prearranged level of operational
performance will be met during a contractual
measurement period ”

http://en.wikipedia.org/wiki/High_availability


Corollary
“ Paradoxically, adding more components to an
overall system design can undermine efforts
to achieve high availability. That is because
complex systems inherently have more
potential failure points and are more difficult
to implement correctly ”

http://en.wikipedia.org/wiki/High_availability


Complexity
is the enemy of
availability


Contrast HA with Disaster
Recovery
• DR triggered by catastrophic loss of primary
data centre (i.e. all or nothing)
• Cost of running a DR site means that more
often now it has a semi-active, or even fully
active, role
• WANs/MANs are getting faster & more
affordable
• => techniques for HA & DR are merging


HA covers failures of…
• Hardware (the most common use case)
– e.g. server failure
– Note: within servers many components are
redundant
(power supplies, disks, sometimes controllers,
NICs/HBAs/HCAs, even memory & processors)
• Software
– unresponsive components


HA does not protect against…
• Loss of data centre
(fire, flood, power, etc)

• Human
error Buncefield, UK Dec. 2005

http://simpsons.wikia.com/wiki/Barney_Gumble


Typical Requirements for HA
• Business:
– An assured level of availability (probably different
between LOBs/applications)
– Environment isolation ( ‘it’s ours’)
– Reduced capital expenditure (esp. licences)
• IT:
– low maintenance
– standard construction
– low complexity
– easy to monitor and troubleshoot


From the ‘Old’ Days to Today
Servers Servers
+ Storage + Storage

Servers Servers

Shared Storage


Just because something is big doesn’t mean it can’t fail!

Virtual Server Virtual Server
Cloud
Shared Storage


High Availability
• HA = as available as your business needs
• Makes things more complicated

• List of HA approaches we’ve used or just
seen… not necessarily complete


Agenda
1. High Availability Outline
2. Generic HA
3. Database HA
4. Middleware HA
5. A Look Ahead & Summary

Generic HA techniques
• Active/Passive Clusters
• Virtualisation Clusters
• Storage Replication


Active / Passive aka Cold Failover
Cluster
• The oldest form of HA
• Primary plus standby server(s)
• Only one server ever active at once
• Active/Passive solutions available from 3rd party vendors,
operating system vendors and Oracle
• A/P plus P/A, or A/P plus -/A for test not unusual
• Advantages
– Simplicity
– Software cost
• Disadvantages
– Hardware cost/power
– Failover time (depending on reqs.)


Active / Passive

Primary Standby

Shared Storage


Active / Passive + - / Active

Primary Dev/Test

Primary Standby Production

Shared Storage

* Note about prod vs test storage


Virtualisation HA
• Relocating virtual machine
– suspend, move, resume
• Automatic relocation
– Move contents of vRAM to target host
– E.g. vMotion, OVM live migration
• Advantages
– Generic across all IT services
– Appears simple
• Disadvantages
– Underlying products don’t know what’s happening
– Support if it all goes wrong


Storage (bit out of scope, but…)
• Replication can be done various ways
– SAN/NAS provider, e.g. EMC SRDF, RecoverPoint, ZFS
– Virtualisation provider, e.g. VMware Storage vMotion
– OS provider, e.g. DRBD
– Probably lots of others…
• Advantages
– Generic
– Elegance in simplicity
• Disadvantages
– May be expensive, especially if need to license both ends
– May be new technology
– Probably sensitive to network stability (latency, throughput)
– “Under the covers” technique the Oracle products don’t know about
– Manual failover? Typically invoking DR procedure.


Active / Passive – Database
Cluster
Protects against server failure
Does not protect against site failure

Consists of
Two servers; one active and one passive
Database files on shared storage
Heartbeat network to monitor cluster health

Under normal operation
Database instances run on active server

On server failure
Passive server becomes active server
Cluster manager fails across all instances to new active server

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©2011 Veriton Limited juliandyke.com

Active / Passive Database
Cluster
Before After
SERVER1 SERVER2 SERVER1 SERVER2

A A A

B B B

C C C
CLUSTER MANAGER CLUSTER MANAGER

STORAGE STORAGE

SITE1 SITE1

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Active / Passive Cluster
Examples
Veritas
IBM HACMP
HP Service Guard
Sun Cluster

Advantages
Administered by system administrators
Only requires Oracle licence on active server

Disadvantages
Administered by system administrators
Under-utilization of hardware
Cluster manager requires licence
Maximum 10 days per calendar year on unlicensed server
Still popular with large users
Some customers downgrading from RAC to active/passive to reduce costs

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Oracle Clusterware HA
Cluster

Consists of
Two (or more) servers
Database files on shared storage - ASM
Application files on shared storage - ACFS
Private network to manage cluster

Instances run on preferred servers

On server failure
Clusterware fails across instances from failed server to surviving server

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Cluster
Before After

A A A

B B B

C C C
ASM / ACFS ASM / ACFS

ORACLE CLUSTERWARE ORACLE CLUSTERWARE

STORAGE STORAGE

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Cluster
Advantages
Administered by database administrators
Based on known and trusted technology stack (Oracle RAC)
Better utilization of hardware during normal operations
Supports non-Oracle applications

Disadvantages
May require additional licences for
Oracle Clusterware
ACFS
Oracle RDBMS

Still relatively rarely implemented
Licencing confused by new Oracle Cloud File System product

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Oracle RAC Cluster

Consists of
Database files on shared storage – ASM
Application files on shared storage – additional cost


On server failure
Instances on failed server are lost
Instances on surviving server remain

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Oracle RAC Cluster
Before After

A A A

B B B

C C C
ASM ASM


STORAGE STORAGE

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Oracle RAC Cluster
Advantages
Known and trusted technology stack
Better utilization of hardware during normal operations
Instances can scale across multiple servers

Disadvantages
Database must be licenced on each server
May require additional licenses for Oracle RAC option
Scaling may affect performance

Business-as-usual clustering solution
Foundation of Exadata and Oracle Database Appliance
Complex to implement, but well understood and reliable in most cases

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Oracle RAC One-Node

Consists of
Database files on shared storage – ASM


On server failure
Clusterware fails across instances from failed server to surviving server

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Oracle RAC One-Node
Before After

A A A

B B B

C C C
ASM / ACFS ASM / ACFS


STORAGE STORAGE

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Oracle RAC One-Node
Advantages
Known and trusted technology stack
Database can be unlicensed on one server
Can be converted into Oracle RAC cluster

Disadvantages
Requires additional RAC one-node licences
Under-utilization of hardware
Maximum 10 days per calendar year on unlicensed server

Really just another licensing option
Rarely deployed in my experience

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Data Guard Physical Standby
Protects against server failure and site failure

Consists of
Two data centres in physically separate locations
Servers and storage at each location
Network between data centres

Instances run on primary servers
Database changes transported from primary server to standby server
Database changes applied to standby server

On server failure
Instances failed over from failed server to standby server

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Before After

A A A

B B B

C C C

STORAGE STORAGE STORAGE STORAGE

SITE1 SITE2 SITE1 SITE2

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Advantages
Protects against site failure
Known and trusted technology
Does not require heartbeat network
Does not require shared storage
Failover can be automated using Data Guard Broker

Disadvantages
Both sites must be licenced
Requires Enterprise Edition database licences
Under utilization of hardware and licences
Applications must be available at both sites
Failover process may be complex – requires testing

Easily the most popular DR configuration
Relatively simple to implement and very reliable when correctly configured

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Active Data Guard
Protects against site and server failure

Consists of
Storage at each location

Read-write instance runs on primary server
Redo transported and applied to standby server
Standby server open for read-only operations
Read-consistency maintained on standby server

On site failure
Read-write instance failed over to standby server

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Active Data Guard
Before After

SERVER1 SER VER2 SERVER1 SERVER2

A A A

STORAGE STORAGE STORAGE STORAGE

SITE1 SITE2 SITE1 SITE2

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Active Data Guard
Advantages
Similar to Data Guard Physical Standby
Better utilization of hardware
Additional read-only capacity
Changes available on standby server in near real-time
Changes only applied on primary server => reduced contention

Disadvantages
Similar to Data Guard Physical Standby
Requires Active Data Guard licenses at both sites
Failover may result in reduced capacity

Simpler architecture to implement than RAC
Performance monitoring and tuning difficult on standby database
Many sites implementing caching functionality in application tier

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Extended RAC Cluster
Protects against site and server failure

Consists of
Shared storage at each location
Storage network between data centres

Instances run on all servers
Database changes are written to storage at both data centres

On site failure
Instances on failed site are lost
Instances remain at surviving site

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Advantages
Better utilization of hardware and licences
Applications maintained at both locations
Reduced failover testing required

Disadvantages
May require RAC licences at both sites
Additional I/O may impact performance
Increased latencies may impact performance
Complex solution requires additional management skills
Oracle commitment to solution is dubious

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And there’s more…
Oracle Restart
Clusterware / ASM on a single server

Replication
Database links / Remote queries
Materialized Views
Advanced Queuing
Oracle Streams
Golden Gate

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Types of Middleware Data
(11g+)
• Binaries
– Read only ($MW_HOME, $ORACLE_HOME)
• Configuration/logs (inc deployed apps)
– Read/write ($DOMAIN_HOME, $ORACLE_INSTANCE)
• State data
– Java Session
– JMS messages
– JTA transactions
• Application data(?)


State data in memory (& on
disk)…
• Java Session objects
– stay in memory (e.g. contents of my basket)
– very common (historical – JVM size)
– replicate to other WebLogic servers using either
WebLogic clustering or Coherence*Web
• JMS messages
– Java messages (e.g. reserve this item in warehouse)
– can choose to store on filesystem or in database
• JTA transactions
– Java transactions (e.g. checkout)
– NEW! WebLogic 12c can choose to store in database


Active / Passive vs Active /
Active
• Active / Active more common in
middleware tier
– Lightweight servers (cd database)
– Processes more likely to fail
– Low interaction between users
– Active / active used for horizontal scalability


WLS 11g A/A +
A/P
Load Balancing or Web Tier

Managed Managed
Server(s) Server(s)
VIP
Admin
Server
Node Mgr Node Mgr

Shared Storage

Note: I prefer to have Admin Servers on a separate management node


Active / Passive CFC & ASCRS
• Oracle Clusterware
– Around since Oracle Database 10g
– (CRS code base much more mature)

• 10g: You must install with everything listening on
VIP
• 11g: ‘transform’ steps
– ASCRS is new “wrapper” (uses Clusterware 11.1), but
its future is unclear to me

• See my UKOUG 2010 presentation:
Building Active/Passive Clusters with Oracle Fusion Middleware 11g
http://www.veriton.co.uk/content/haslam_events.shtml


Active / Passive CFC
VIP

iAS
OC4J
Primary Standby

OPMN

Shared Storage


WLS Whole Service/Server
Migration
• Service or Server running against VIP
• Node Manager co-ordinates service or
server restart with Admin Server


Whole Server Migration
VIP

WLS

Primary Standby
Node Node
AS Mgr Mgr

Shared Storage


HA for Layered Products
• More difficult
• Mainly application level clustering (e.g.
OIM, OAM)
• Legacy products little, or product-specific
options
– Chunks of C code
• Newer products:
– With SOA/BPM 11g uses Coherence for HA
– Needs to co-ordinate with database failover
Note: 10g AS Guard has gone – more generic approach now ☺


• Hardware HA – traditional, simple
active/passive
• Database HA – Oracle products
• Virtualisation HA – treat with caution
• Middleware HA – review in ‘WebLogic
world’


Thanks for listening!

Twitter: @simon_haslam
Blog: http://simonhaslam.co.uk

info@juliandyke.com
Twitter: @julian_dyke
Blog: http://juliandyke.wordpress.com


High Availability Options for Modern Oracle Infrastructures

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