Hard Data sells custom and pre-built Raid boxes and systems.
Why RAID?
There are two reasons to use RAID:
Redundancy / Performance
Some RAID levels provide excellent redundancy while others provide excellent performance. Many levels may combine the redundancy with the performance to achieve a happy medium. By using a hardware raid controller, you may also support live hot swap of drives. In some cases a RAID controller will support automatic rebuilds of replaced drives to minimize downtime and administrative work.
Multiple Channels
Some models of RAID controllers have multiple channels, for disks and/or hosts, allowing for multiple hosts, redundant host connections, multiple disk channels for larger capacity and higher performance.
RAID Levels
- RAID 0 - Employs striping to provide faster performance. Striping splits the volume's blocks across 2 or more disks to provide better performance. Highest Bandwidth, no Fault Tolerance
- RAID 1 - Mirrors everything from on disk to another. This provides Full Redundancy. High Availability
- RAID 3/4 - Data is striped across volumes with stripes parity stored on separate drive(s). High Bandwidth, Fault Tolerance
- RAID 5 - Independent disks with parity striped across the volumes. Versatile, Good Bandwidth, Fault Tolerance
- RAID 6 - Similar to RAID 5, this newest level provides an n+m solution allowing for failure of m drives before data loss. Due to the complexity of the parity scheme, only n+2 is provides a practical solution.
- RAID 10 - Data is striped across mirrored sub-arrays. High Bandwidth, High Availability
- RAID 0+1 - Data is mirrored across RAID 0 sub-arrays. High Bandwidth, Some Fault Tolerance
- RAID 30 - Data is striped across RAID 3 sub-arrays. Increases Bandwidth.
- RAID 50 - Data is striped across RAID 5 sub-arrays. Increases Bandwidth and Fault Tolerance.
- JBOD - Just a Bunch Of Disks - This is not raid but is supported by most raid controllers. It can combine several disks of varying sizes into one large volume or just use them as a bunch of extra drives. Why would you use this over RAID O? RAID O is limited in size to the number of drives times the size of the smallest drive where as JBOD is the sum of the drive sizes.
(c) 2003 Hard Data Ltd. webmaster@harddata.com
| STORAGE | SOFTWARE | PC CASES | WHAT IS? | NETWORKS | CONTACTS |
| SUPPORT |