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U N D E R S T A N D I N G S Y S T E M R E D U N D A N C Y
B Y J O S H N E L A N D A N D F R A N K L I N F L I N T
Beyond Controllers andCapacitors
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Fast Forward
Evaluate redundancy opportunities within systemand subsystem software.
Eliminate single points of failure in hardware
infrastructures. Configure redundancy in servers, power, cooling,
and networking.
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S T A R T A T A H I G H L E V E L W I T H T H E S O F T W A R E
E N V I R O N M E N TD E T E R M I N E A S T R A T E G Y F O R B U I L D I N G T H ER E Q U I R E D A V A I L A B I L I T Y L E V E L S I N T O T H EV A R I O U S S U B S Y S T E M S
Clustering software enables automatic failover from afaulty node to a different node in a cluster.
Virtualization allows different types of software stacksto be managed in a uniform way.
Match the responsiveness of a chosen solution to therequirements during the design phase.
Nodes should minimize state and fail gracefully.
Building High Availability
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Active/Active Active/Passi
The primary and reservenodes are running the
database at any giventime
Low failover latency Easy expansion
Load balancing Requires nodes to be
designed so they can runconcurrently
Provides a fully redundantnode for each operationalnode in the system
The redundant node isbrought online only if theactive node fails
Simpler to implement Cost of providing a fully
redundant set of nodes(and hardware) can be high
Active/Active and Active/PassiveConfigurations
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The difference
betweenDedicated and
Multi-purposedNodes
With dedicated nodes,you must decide howmany redundant nodesto provide for eachinterface.
With multi-purposednodes, a single sharedpool of extra nodes canprovide the redundancyfor any of the interfaces.
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Evaluating Required Interface Behavior
Make external interfaces highly available byimplementing a retry policy internally acrossredundant nodes of any subsystem.
Design the system to achieve availability at theunderlying storage level.
All the subsystems should access shared, centralizedstorage.
Replicate databases and regularly update the copies.
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Configuring Hardware for Redundancy
Hardware redundancy startswith the selection of servertechnology.
Blade servers are more space-efficient and energy-efficientthan equivalent stand-alonerack servers, and blades areeasy to slide into a chassis toquickly add processingcapacity or swap out a faultyunit.
Redundant hardwarecomponents can include: Redundant and hot-pluggable
chassis cooling fans
Redundant chassismanagement modules
Standard N-1 redundant hot-plug power supplies
Optional redundant RAM
Redundant storage with hot-plug hard drives
Battery backed-up RAID cache Redundant network interfaces
Redundant hot-plug switchmodules
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Blade Servers
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R E V I E W T H E A V A I L A B L E C O N F I G U R A T I O N
O P T I O N S F O R V A R I O U S F U N C T I O N S setting up a redundant configuration can simply require
installing modules and powering up the system
Or it may require using a management interface toconfigure the redundancy options.
A M O N G T H E M O S T C O M M O N P O I N T S O F F A I L U R E
I N A N Y S E R V E R A R E T H E H A R D D R I V E S
Server Configuration
Options
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ProvidingBackup for
Power,Cooling
Organizations wantinga true high-availability
solution shouldconsider purchasingpower from twodifferent utilitycompanies.
Each blade server enclosure containsmultiple chassis power supplies
Redundancy allows uninterruptedsystem operation if one or more ofthese chassis power supplies fails
Administrators can also configurethe management interface to turn off
server blades based on theorganizations priorities The blade chassis cooling system,
which consists of multiple fanmodules, is an important factor
A well-designed blade chassis willprovide hot-pluggable fans withmore cooling potential than isnecessary for the platform
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Ensuring Redundancy
Well-designed blade servers ensure networkconnection redundancy
Chassis designs also allow installation of dual
Ethernet switch modules that can enable additionalconnectivity or network redundancy and faulttolerance
A distinction between a blade server and others is
that the connection between the NIC or LOM and theinternal ports of the switch module is hardwiredthrough the midplane
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Deciding Where to Invest
As infrastructure grows increasingly integrated andintelligent, companies have an opportunity to changethe architecture of their systems
This way, availability does not depend on every singleprocessor and capacitor, but is also built into databases,interfaces, and applications
Be selective about where to invest in redundancy
Start with the overall system, assess which subsystems arerequired to be highly available, and consider the softwareenvironment as well as the hardware domain
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ABOUT THE AUTHORS
Josh Neland and Franklin Flint are Technology Evangelists for theOEM Solutions group at Dell. You can follow their musings on Twitter@joshneland and @franklinAtDell, and read more of their work athttp://blog.delloem.com/
http://blog.delloem.com/http://blog.delloem.com/http://blog.delloem.com/8/4/2019 Dell OEM Beyond Controllers and Capacitors Power Point
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Resources
http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/
http://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-
appliances-program.aspx
http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://content.dell.com/us/en/enterprise/oem-industry-solutions-oem-appliances-program.aspxhttp://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/http://blog.delloem.com/2011/08/article-on-redundancy-written-by-our-dell-oem-technology-strategists-on-intech/