RAID TECHNOLOGY

There are a number of possible RAID Levels that can be used individually or in combinations according to your server needs. For example within a single server system 2 hard drives might be placed in a RAID 1 array and the operating system loaded on it, and another 3 drives setup in a RAID 5 and used for data storage (for a database or web server). Below is a table of the most common configurations.

Raid Level	Definition	Min.# Drives	Advantages	Disadvantages	Uses
RAID 0	Striped disk array - the data is broken down into blocks and each block is written to a separate drive	2	Faster Performance	No Fault Tolerance	Video Editing, High Bandwidth I/O Applications
RAID 1	Mirrored disk array - second drive is exact copy of first drive	2	Simple to setup, Fault Tolerance	Less Efficient	Applications / Servers Requiring High-Availability
RAID 0+1	Two striped arrays that are mirrored with each other	4	Fault Tolerant, High I/O performance due to striping	Limited scalability	Workstation, File Server
RAID 5	Striping plus parity - data written across all drives in array	3	Fault Tolerant, fast data reads, good for hot swap	Takes longer to rebuild than RAID 1	Database, Web, E-mail, and News servers
RAID 50 (5+0)	Data is “striped” across multiple drive groups (super drive group). For data redundancy, drives are encoded with rotated XOR redundancy	6	RAID 50 provides high data throughput, data redundancy, and very good performance	Requires 2 to 4 times as many parity drives as RAID 5.	Database, Web, E-mail, and News servers
JBOD	"Just a Bunch of Disks" - spanned volume	2	Can create larger partitions from odd size drives	No fault Tolerance, no performance increase	Temporary extra storage space (non critical data)

Advantages of using RAID Technology

RAID is a very important technology for both servers and business workstations and you must educate your customers on why it is a good investment for them. The primary advantages of RAID:

1) Data is your customer's most important resource and cannot be easily replaced like hardware.

2) Downtime for a business or an individual who losses important data is costly. RAID can protect that data and save time and money. Remember there is NO TIME for DOWNTIME!

3) Backing up data to a CDR or tape drive is good for longer-term storage but does not offer immediate real-time redundancy of data and software like RAID can.

4) Certain RAID configurations can not only protect data but also increase performance and make it easier to expand storage in the future.

For information on RAID management software (which comes bundled with most retail package RAID cards) see: Server Software + Operating Systems

Intel® RAID Controllers Compatibility Matrix: http://support.intel.com/support/motherboards/server/compat_matrix.htm