An Investigation into Transport Protocols and Data Transport ...

A.1. Data Storage 262
absolutely no fault tolerance and the failure of just one drive will result
in all data being lost.
• RAID-1: Also known as mirroring. Total redundancy is provided by
writing identical data to multiple disks, and therefore requires at least
two hard drives. As the data is written just once (and mirrored) there
is no improvement in write times over a single hard disk. However, as
the data is distributed over pairs of disks an improvement of two times
the single drive read speed can be achieved. As each pair of disks is
mirrored, there is no performance increase as the number of disks used
increases. However, as there is 100% redundancy of data, no rebuild
is necessary in case of a disk failure and a simple copy of data to the
replacement disk is required.
• RAID-10: Combines striping and mirroring, thus providing high performance
read write speeds and total redundancy. It is implemented
as a striped array who segments are RAID-1 arrays. As such it has
the benefits of performance and fault tolerance of both RAID-0 and
RAID-1 systems. However, the use of so many disk drives means that
the cost is high as storage capacity is low. In many ways RAID-10 is an
ideal solution for high speed, fault tolerant data transfer and storage.
• RAID-5: Writes data in stripes similarly to RAID-0, but also checksums
the data and creates parity blocks in the same rank on writes.
These are distributed across the total number of disks alongside the ordinary
data stripes. It requires a minimum of three disks to implement.
In the event of a single disk failure the ordinary data can be recovered
using the parity data. This configuration gives high redundancy to-