CHAP 8.1 Business Continuity Flashcards
what is business continuity
set of related activities targeted to ensure:
- critical business functions will continue to operate despite major disruption
- ability to recover operation within short period of time after major incidents
objective is to MINIMIZE OUTAGE TIME
impacts of downtime
- loss of revenue
- damaged reputation
- loss of productivity
key elements of business continuity
- resilience
- recovery
- contingency
high availability
- no downtime
- alw avail 24/7
loss of availability
outage/downtime
types:
- planned (eg maintenance)
- unplanned (eg offline, slow response)
common threats to availability
- disease
- earthquake
- fire
- cyber attack
high availability requirements
- no. of users affected
- no. of external customers affected
- available budget
HA technologies
- fault-tolerant & redundancy: use fault-tolerant components to improve redundancy
- network load balancing: distributes application requests among multiple nodes
- failover clustering: migrates services from one server to another when the server fails
- VM migration: moves a VM to a new host wo shutting it down
fault-tolerant components
fault-tolerant components IMPROVE REDUNDANCY
eg:
- SAN STORAGE w duplicate power supply unit, nwk cabling
- disk configured w RAID support hot-swap
RAID 0
- striped set
- data written across ALL disks in 64kb units (striped)
- provides performance but not fault-tolerant
- storage efficiency: 100%
RAID 1
- disk mirroring
- simultaneously writes data to two volumes on two physical disks
- almost any volume can be mirrored, incl the system and boot volumes
- storage efficiency: 50%
RAID 3
- striped set w dedicated parity disks
- parity data used to recover missing data if one disk is down
- parity data is written on a dedicated disk
- requires MINIMUM 3 DISKS
- storage efficiency: (n-1)*100/n (n=no. of disks)
RAID 5
- striped set w distributed parity
- requires MINIMUM 3 DISKS
- storage efficiency: (n-1)*100/n (n=no. of disks)
RAID 6
- striped set w dual distributed parity
- use parity to recover missing data from UP TO 2 FAILED DISKS
- require MINIMUM 4 DISKS
- storage efficiency: (n-2)*100/n (n=no. of disks)
RAID 1+0
- nested RAID
- data is mirrored then striped
- require MINIMUM 4 DISKS
- storage efficiency= 50%
network load balancing
- scalable HA technology
- balances traffic based on node utilization
- provides scalability as more servers can be added
- provides availability when:
- server failure is detected
by other servers in the cluster
- failed server load will be automatically distributed among other servers in the cluster
requirements to implement NLB
all nodes must:
- have the same configuration
- data can be stored in a central location
- data can be synchronized between servers
failover clustering
- provides fault-tolerance by ensuring availability of critical services
- computers (nodes) are setup as a cluster
- requires private nwk which is shared by the cluster nodes and is used to monitor each node’s status and communicate w each other
- clustered services and resources are moved from one node to another when a node becomes inactive or fails
- cluster service can fallback after the offline node becomes active again
- usually implemented as part of a load balancing process
when to use failover clustering?
- when HA is required
- scalability is not required
- application uses IP-based protocols
- client or protocol can automatically reconnect to the application
hyper-v replica
- allows for host-based replication of VMs wo the need for any shared cluster components
- uses AD or certificate based authentication for security
- once VM has been replicated, it can be powered off and powered on to carry out planned or unplanned failover
live migration
- moves running VMs from one physical server to another w no impact on availability for users
- pre-copies the memory of the migrating VM to the destination server
- no special configuration needed for the guest OS
- provides HA
DHCP service HA
- dhcp servers share dhcp scope and lease info to ensure continuous availability
- configured using dhcp failover
DHCP service HA failover modes
hot standby mode:
- secondary server will take over when primary server is unavailable
load balance mode:
- both servers dhcp clients
- requests are load balanced between servers
cold backup site
- provides office space only
- takes longer to get into full operation
- least expensive
hot site
- fully staffed and includes all equipment, software and communications facility
- can take over operations quickly
- most expensive
warm site
- site may be installed w most of the equipment and facility preconfigured for operation
- needs time to recover and start operation
