5. Implement High Availability Flashcards
RPO
Recovery Point Objective
The amount of data that must be restored in the event of a failure
RTO
Recovery Time Objective
The length of time an application can be unavailable before service must be restored
MTBF
Mean Time Between Failure
MTTR
Mean Time To Recover
Failover Clustering
Used for applications and services such as SQL and Exchange
Network Load Balancing
Used for network-based services such as Web, FTP and RDP servers. Allows configuring two or more servers as a single virtual cluster.
NLB Unicast Mode
- Cluster adapters for all nodes are assigned the same MAC address.
- Can cause subnet flooding since all packets are sent to all ports on the switch.
- Communication between nodes is not possible.
NLB Multicast Mode
- Cluster adapters for all nodes get their own MAC address
- Nodes are assigned a multicast MAC address (from IP of cluster)
NLB IGMP Multicast
Similar to multicast, but prevents switch flooding because MAC traffic only goes to ports of NLB cluster
IGMP
Internet Group Management Protocol
NLB Stop
Cluster stops immediately, all active connections are killed
NLB Drainstop
Cluster stops after answering all current connections, no new connections are accepted.
Hyper-V Replica
Replicates VMs from primary site to secondary site simultaneously
Extended (Chained) Replication
Host 1 > Host 2 > Host 3 Does not support application-consistent replication
NLB Affinity Types
- None
- Single
- Class C
NLB Affinity: None
NLB does not assign clients to a node, all requests can go to any node
NLB Affinity: Single
Single Affinity allows a client to be assigned to a single node. Best intranet performance.
NLB Affinity: Class C
NLB links clients with a specific node based on the Class C part of the client’s IP address. Best internet performance.
NLB Cluster Requirements
- Adapter can only support TCP/IP
- Servers in cluster must have static IP’s
Test Failover
Verifies a replica can start in the secondary site
Planned Failover
Used during planned downtime. Primary VM is powered off and replica is powered on and syncs changes to primary. Normal primary is restored after failover is complete.
Unplanned Failover
Only initiate if primary machine is offline.
DHCP Guard
Drops DHCP server messages from unauthorized VMs pretending to be a DHCP server.
Router Guard
Router Guard drops advertisement and redirection packets from unauthorized VMs pretending to be routers. Similar to DHCP Guard.
Protected Network
Virtual machine will be moved to another cluster node if a network disconnection is detected.
Port Mirroring
Allows VM network traffic to be monitored by copying packets and forwarding to another VM for monitoring
NIC Teaming
Place NICs in a team in the guest operating system to aggregate bandwidth and provide redundancy. Useful if teaming is not configured in management OS
Device Naming
Causes the name of the network adapter to be propagated into supported guest OSes
VM Checkpoints
System state backup of VM from specific point in time
Software Load Balancing
Allows having multiple servers hosting same virtual networking workload in a multitenant environment.