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Reasons to love Exchange 2013 High Availability. Steve Goodman Exchange MVP Senior Consultant at Ciber UK Twitter - @ stevegoodman Email – steve@goodman.net Web – www.stevieg.org . Reasons to love Exchange 2013 HA.
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Reasons to love Exchange 2013 High Availability Steve Goodman Exchange MVP Senior Consultant at Ciber UK Twitter - @stevegoodman Email – steve@goodman.net Web – www.stevieg.org
Reasons to love Exchange 2013 HA • This evening we’ll cover a few great features that I think make Exchange 2013 a no brainer • It’s an informal session so feel free to add your point of view and favourite features! • Let’s start with a brief history of Exchange HA…
Evolution of HA in Exchange A very brief history
No CAS session affinity required • Clients can connect to any CAS and remain connected to the same session • Requires the same SSL certificate on each CAS • Builds on the every server is an island principle • Makes load balancing much simpler
Unbound Namespaces • Site Resilience typically required lots of names • Unbound allows you to have a single name across multiple sites (i.e. not bound to a site) • Use no affinity round robin to balance across Load Balancer VIPs • Although not essential, Geo DNS can ensure clients stay in-region
3. Two and a half sites AKA File Share Witness in a Third Datacentre
Third Datacentre File Share Witness • Even number DAGs use a File Share Witness to maintain quorum • In Exchange 2010 a typical deployment included a primary File Share Witness in the Primary DC, and Alternative FSW in a secondary DC. • As part of Site Resilience procedures, the Alt FSW would be activated manually
Third Datacentre File Share Witness • Exchange 2013 allows a third datacentre to be used for the File Share Witness • This must be well connected to both datacentres • In the event of a single DC loss, quorum is not lost • Azure IaaS may be supported in the future
Dynamic Quorum • Part of the Windows Clustering Stack and introduced in Server 2012 and enabled by default • Effectively allows the DAG to continue operating even after the point it would normally lose quorum, even down to a single node • Helps to withstand planned shutdowns
Database Auto Reseed • JBOD has been supported since Exchange 2010 and is a foundation for Exchange Native Protection • The theory is you have enough Database Copies to remove the need for hardware RAID • In Exchange 2010, a failed disk must be partitioned mounted and formatted, then the database must be reseeded manually and progress monitored
Database Auto Reseed • Database Auto Reseed complements technologies including JBOD, multiple databases per volume and loose truncation • The DAG is designed with online spare disks and mount points for both databases and volumes • In the event of a disk failure, the spare disks are automatically brought online and databases reseeded from other copies
How are these features used in Office 365? • Microsoft run Office 365 in 26 locations, worldwide • Over 125,000 Mailbox Databases, thus.. • Over 80 DAGs • Over 1200 Exchange Servers • Potentially a lot more DAGs and servers • Global scale requires automated recovery from failures and simplicity where possible
How are these features used in Office 365? • Round robin DNS used for no session affinity when accessing outlook.office365.com • An unbound namespace along with geo-DNS used for outlook.office365.com • A third site out of region is used for every Exchange Online DAG • Dynamic Quorum is on by default in Office 365
How are these features used in Office 365? • Dynamic quorum is used by default in Office 365 to help increase availability • Database Auto Reseed was born in the service as it becomes impossible to manually change disks, then perform and monitor reseeds at global scale
Putting it together Yes, you can try this at home!
Putting it together • You can design a super resilient architecture that can service datacentre failures with little to no customer impact • Microsoft’s Preferred Architecture provides the best starting point when thinking about the best way to put this together