Fail-safe Equipment

Fail-safe Equipment Corporations today budget for the purchase of extra servers for the main servers for their organization. These extra servers are configured so that they will automatically take over functionality if the main servers stop processing services due to outside attacks or even hardware failures. Any event or transaction that occurs in the main server is continuously replicated to the hard-drive memory of the redundant servers. This replication allows for either server to take control when one of them fails. The dis-advantages for this concept is the extra cost of equipment, additional maintenance, and the need for constant testing in order to verify functionality in case of emergency. Another form of fail-safe equipment is a server that has been built with Redundant Array of Independent Drives (RAID). This design combines multiple disk drives in order to distribute data across them in several different levels. The levels are based on standard schemes that have evolved over time.
Pros
Improve performance and storage
Data is written identically to two drives
Read request is serviced by either drive
Must have at least two drives but may have others as long as there is an even amount of drives
Array continues to function as long as one drive is still running

Cons
No fault tolerance
Any drive failure destroys the RAID
Not necessarily safe
Systems with “Write caching” turned on has an illusion of higher performance but may not write all data
Power failure can leave the drives in an inconsistent state or even unrecoverable
RAID 10
Data is written in stripes across the primary disks and mirrored on the secondary disks
Consists of four drives typically
Combines the best concepts of RAID 0 and RAID 1
Better performance and reliability
The following RAID drive configurations follow the same concepts as the RAID 10 design.
RAID 2
RAID 3
RAID 4
RAID 5
RAID 6
The disadvantage to this style of configuration is that there is an added

References: Beasley, J. (2009). Networking (2nd ed.). Boston: Pearson Education, Inc. Mansfield, K. & Anthonakos, J. (2010). Computer Networking from LANs to WANs: Hardware, Software, and Security. Boston: Course Technology.