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Welcome to Exam Notes by CertBlaster. This edition covers Network Plus N10-007 Objective 3.2 “Compare and contrast business continuity and disaster recovery concepts.” You could be tested on any of the bolded terms. If you are unsure about any terms do further research.
Fault tolerance plays a critical role in maintaining network availability. Simply put faults lead to failures and failures are not acceptable. Your goal is to have the highest network uptime. So here we will look at some of the practices that reduce faults and thereby minimize or circumvent failures.
Redundancy enables your network to remain up in the event of a failure. Redundancy takes several forms in this area. It could be a Battery backup/UPS on critical devices or even a power generator onsite to provide reliable power during an outage. Your UPS will protect your equipment against power anomalies like blackouts, brownouts, and surges. It also will provide clean power that is free from electrical noise or EMI.
Your server itself can have dual power supplies installed. The second power supply will take over if the primary one fails.
Within the server(s) you can use a Redundant Array of Independent disks (RAID) configuration. RAID can tolerate a disk failure and continue to operate normally. The failed disk can be replaced and automatically be restored without service interruption.
Everything fails or needs to be replaced, that’s a fact. Your inventory management software should include the date equipment was put in use. You should be aware of two factors that will help in planning preventative maintenance. You will define the time expectancies in the SLA (Service Level Agreement).
MTTF (Mean Time Between Failure) Is the predicted operational life of a device before it fails. This is based on manufacturer testing. This metric is quite useful as equipment nears the end of its life expectancy, you can plan replacements or upgrades.
MTTR (Mean Time To Repair) As the name implies this is the average time it will take to repair an outage condition. Your ISP will define these times in your SLA.
High availability (HA) is a term used to identify the uptime of a network. Availability is measured as an average percentage. Downtime is calculated and then rated. For example, a system that functions reliably nearly all the time may be rated as 99.999% which equates to about 5 minutes a year downtime or less than 30 seconds a month. Compare that to a network rated at 99% which will be down roughly 8 hours a month.
The availability is you require relative to your business needs and budget. Your SLA with customers is an important consideration here. The more 9’s your network supports the higher the equipment cost and technical support you will need. A four 9’s network will be down 8 seconds a day or less than an hour per year on average. A five 9’s network will average out to around .4 seconds a day.
An essential element of availability is to eliminate a single point of failure. Redundant circuits prevent a switch or firewall failure from bringing the network down.
On the devices NIC teaming allows you to configure two or more NICs in a Windows device and have it appear as a single logical interface. On Cisco devices, this method is called port aggregation. Whatever you call it performance is increased as this practice provides higher throughput, failover protection, and practical load balancing.
In a case where you have a Webserver, you will need at least one identical server. Both servers can be configured as a cluster. The cluster will appear as a single device If it is online using a dedicated load balancer will intelligently distribute the traffic intelligently maximizing your performance in peak periods.
A good disaster recovery plan is essential to business continuity. The recovery option you use will depend on several factors like planning, cost, hardware, software and the level of employee involvement required. You will always deploy your recovery site in another location. This could be a different building or another geographic location. There are three types of recovery sites:
Cold Site – This site will contain all of the hardware and software necessary to restore operations. The devices are not configured or connected. You have the task of installing the OS(s) on the server(s) and configuring it. This is true for all routers and switches necessary, representing a considerable amount of time and effort. It is the least expensive option and takes the longest time to recover.
Warm site – A warm site can be brought online more quickly than a cold site. The warm site will contain all of the hardware and software. It will be updated regularly, but not necessarily often. The updates to the site may be monthly and any interim restoration will require recent data to be retrieved from backups. This is still quicker than a cold site restoration.
Hot site – The fastest recovery method is the hot site. This site has all of the hardware and connectivity is up to date and ready to be deployed. There is minimal downtime. Your servers can be configured to mirror data to these sites. This is the most expensive option.
Backups – When planning backups, you need to know what needs to be backed up and how often it should be backed up. We cover four backup types here:
Full backups back up everything each time it is performed.
Differential backups back up everything that has changed since the last full backup.
Incremental backups back up everything that has changed since the last backup.
Snapshots can’t replace the backup types outlined above. They are very useful for frequently used files. The snapshots are taken frequently, even while the files are being modified. Consider it as a frequent incremental backup.
That’s all for objective 3.2! You’re half-way through Main Domain 3.0. Good luck on the test!
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