Module 9 - Business Continuity

BC

the process of preparing for and recovering from system outages to keep operations running smoothly

• Ensure continuous access to data and services

• Use proactive/reactive measures

• Automation to reduce downtime and manual effort

• Main goal is to maximize availability of apps and info

• Ex: if a natural disaster caused a power outage, a good BC plan ensures power kicks in or shifts operations to another data center to keep services running

Information Availability

the ability of an IT infrastructure to function according to business requirements and customer expectations, during its specified time of operation.

IA can be defined in terms of:

accessibility, reliability, and timelines

accessibility

information should be accessible to the right user when required

reliability

information should be reliable and correct in all aspects. I tis the same as what was stored and there is no alteration or corruption to the information

Timelines

defines the time window during which information must be accessible

Causes of information Unavailability

• Application failure

• Data center outage

• Refreshing IT infrastructure

• Infrastructure Component Failure

• Data Loss

planned outages

such as installation and upgrades, facility constructions

unplanned outages

such as human error or natural disaster

impact of information unavailability

lost productivity, lost revenue, financial performance, other expenses, and damaged reputation

MTBF

mean time between failure

average time for a system to perform its normal operations until another failure

total uptime/number of failures

MTTR

average time is takes to repair a failed component

total downtime/number of failures

IA formula

IA = MTBF / (MTBF + MTTR) or IA = Uptime / (Uptime + Downtime)

RPO

Recovery Point Objective

point in time to which data must be recovered

RTO

Recovery Time Objective

Time within which systems and applications must be recovered

units of RPO and RTO

both are counted in units of time

usually the lower the RTO and RPO

the higher is the cost of a BC solution

Disaster Recovery

involved a set of policies for restoring IT infrastructure

the fundamental principle of DR

maintain a secondary data center or site called a DR site which should be located in a different geographical region

BC Technology Solutions

• implementing FT mechanisms

• deploying data protection solutions

• automatic failover mechanisms

• architecting resilient modern applications

Fault Tolerance

the ability of an IT system to continue working in the event of a failure

Key Requirements for FT

fault isolation and eliminating SPOF

Fault Isolation

contains the scope of a fault so that the other areas of a system are not impacted by the fault.

Single Point of Failure

refers to any individual or aspect of an infrastructure whose failure can make the entire system or service unavailable

How to eliminate SPOF

implement redundancy at component level: compute network storage

implement multiple availability zones

Network FT Mechanisms

link aggregation

NIC teaming

Multipathing

Elastic Load Balancing

link aggregation

combines link between 2 switches/nodes to enable network traffic failover

NIC teaming:

groups NIC so that they appear as a single logical NIC to the operating system or hypervisor

Multipathing

enabling a compute system to use multiple paths for transferring data to a LUN

Elastic Load Balancing

detecting the unhealthy VM instances and automatically redirects the I/Os to other healthy VM instances.

Storage Fault Tolerance Mechanisms

RAID

Erasure coding

Dynamic Disk Sparing

Cache protection

Erasure coding

•  provide space optimal data redundancy to prevent data loss against multiple disk drive failures

  • Set of n disk divided into m disk to hold data and k disks to hold coding infos

    

Dynamic Disk Sparing:

hot spare

Cache protection

- mirroring

Erasure Coding

Provides space-optimal data redundancy to protect data loss against multiple drive failure

Cache Protection - Mirroring

Each write to cache is held in two different memory locations on two independent memory cards. • If a cache failure occurs, the write data will still be safe in the mirrored location and can be committed to the storage drive

FT at Site-Level - Availability Zones

Availability zone is a location with its own set of resources and isolated from other zones

Dell EMC PowerPath

a family of software products that ensures consistent application availability and performance across I/O paths on physical and virtual platforms. • PowerPath provides automated path management and tools that enable you to satisfy aggressive service-level agreements without investing in additional infrastructure