RAID (Redundant Array of Independent Disks) Raid 0, 1, 5, & 6

 

RAID

(Redundant Array of Independent Disks)

RAID 0:

RAID 0 provides no fault tolerance or redundancy. Requires a minimum of 2 disks. The information is spread across each drive (for example, as it fills one block and then adds data to the next sequential block). 

RAID 0 is striping with no parity. If one drive fails, all the information is lost without a data backup.

This form of RAID is used for performance, with multiple heads reading/writing simultaneously.

Both drives should be the same size and speed. If you have two 320 GB drives, theoretically, this configuration would give you 640 GB of storage space. 

RAID 0 is best used for video and audio streaming. It could also be used for something like a backup server. The backups are stored on other media than the backup software system. 

RAID 1:

RAID 1 requires 2 drives and is known as mirroring. The exact same data is written to both drives. With RAID 1, you can add another disk controller, eliminating a single point of failure. Using two disk controllers in this configuration is known as duplexing.

Theoretically, if you use two 320 GB drives, you will have 320 GB for storage. 

If one drive fails, all the data is retained on the other drive. the performance will NOT degrade if one disk fails. You must not shut down this system to replace the failed drive. Simply remove the drive, remove it from the sled/carrier, and replace it with a new one. Reinsert the drive, go to the console, and select resync array. 

Use this RAID configuration for operating systems and authentication servers. etc. You have minimal drive space to work with. 

RAID 5:

RAID 5 requires a minimum of 3 disks and is striping with one parity stripe. The equivalent of one drive is used for the parity information. This helps provide fault tolerance.

RAID 5 has great read performance, as multiple heads read simultaneously. As the number of drives increases, so does the read speed. However, write performance is slow due to the parity calculation on the full stripe. 

This RAID setup can afford the loss of only one drive. In more than one drive, the data is lost. Remove the failed drive while the system is operational, install a new drive, go to the console, and select regenerate array. The performance will degrade as it rebuilds the array. 

If you have three 320 GB drives, you will have 640 GB of storage space, as the parity data will take up the equivalent of one drive.

RAID 6:

  

RAID 6 requires a minimum of 4 drives. It is configured as striping with dual parity. The equivalent of two drives is used for the parity information. This setup provides fault tolerance.

It has great reading speed, as multiple heads are reading simultaneously. However, write speed is even slower than RAID 5, as RAID 6 has to calculate dual parity for each stripe. 

RAID 6 can survive the failure of two simultaneous drives. Again, take out the failed drives or dives and replace them with new drives. After reinserting the drives, go to the console and select rebuild array. 

Four 320 GB drives in a RAID 6 will give you 640 GB of storage space.

Read speed gain

RAID 0     =      2x

RAID 1     =      2x

RAID 5     =      2x

RAID 6     =      2x

RAID 10   =      4x

 

Write speed gain

RAID 0     =      2x

RAID 1     =      1x

RAID 5     =      1x

RAID 6     =      1x

RAID 10   =      2x