Various Types of RAID
RAID stands for Redundant Array of Independent Disks and is widely used in commerical sectors. Using a RAID storage subsystem has the following advantages:
- Provides disk spanning by weaving all connected drives into one single volume;
- Increases disk access speed by breaking data into several blocks when reading / writing to several drives in parallel operations. With RAID, storage speed increases as more drives are added;
- Provides fault-tolerance by mirroring or parity configuration.
Common terms that you will need to understand more include:
NRAID stands for Non-RAID. The controller treats each drive as a stand-alone disk, therefore each drive is an independent logical drive. NRAID does not provide data redundancy.
JBOD stands for Just a Bunch of Drives. The capacity of all the drives is combined to become one logical drive (no block striping). In other words, the capacity of the logical drive is the total capacity of the physical drives. JBOD does not provide data redundancy.
RAID 0 provides the highest performance but no redundancy. Data in the logical drive is striped and distributed across several physical drives on the same volume.
RAID 1 mirrors the data stored in one hard drive to another. RAID 1 can only be performed with two hard drives. If there are more than two hard drives, RAID (0+1) will be performed automatically.
RAID (0+1) Disk Striping with Mirroring. This configuration combines RAID 0 and RAID 1 - Mirroring and Striping. RAID (0+1) allows multiple drive failure because of the full redundancy of the hard drives. If there are more than two hard drives assigned to perform RAID 1, RAID (0+1) will be performed automatically.
RAID 3 Disk Striping with Dedicated Parity Disk. One drive member is dedicated to storing the parity data. When a drive member fails, the controller can recover / regenerate the lost data of the failed drive from the dedicated parity drive.
RAID 5 Striping with Interspersed Parity. RAID 5 is similar to RAID 3 but the parity data is not stored in one dedicated hard drive. Parity information is interspersed across the drive array. In the event of a failure, the controller can recover/regenerate the lost data of the failed drive from the other surviving drive.
Fully understanding the physical storage configurations is a must for better manage and control your data storage strategic and emergency planning.
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