RAID: A Quick Summary
RAID levels: what do they mean? There are thousands of words on the subject, so here's a quick summary.
RAID0: Just disk striping. No real redundancy here, just an array of disk which are striped (at a defined size) so that files are spread out across the disks in the array. Low cost, but not for important data - needs to be backed up though...
RAID1: Mirroring. Data is duplicated on 2 different drives in the array. Provides some fault tolerance.
RAID2: Weird one. Does bit-level striping. Not used these days.
RAID3: Does byte-level striping with dedicated parity. Dedicated Parity is where a calculation is done on the data and stored on a dedicated parity disk so that the original data can be rebuilt if something goes wrong. Used for large files, multimedia, etc.
RAID4: Block-level striping with dedicated parity. Like RAID3, but not commonly used.
RAID5: Very popular choice. Block-level striping with distributed parity. Both data and parity is distributed across all the drives in the array. Removes bottleneck of a dedicated parity disk. Probably best overall choice unless the environment is write-heavy.
RAID6: as RAID5, but dual distributed parity. This means that two sets of parity info are calculated - adds extra fault-tolerance.
RAID0: Just disk striping. No real redundancy here, just an array of disk which are striped (at a defined size) so that files are spread out across the disks in the array. Low cost, but not for important data - needs to be backed up though...
RAID1: Mirroring. Data is duplicated on 2 different drives in the array. Provides some fault tolerance.
RAID2: Weird one. Does bit-level striping. Not used these days.
RAID3: Does byte-level striping with dedicated parity. Dedicated Parity is where a calculation is done on the data and stored on a dedicated parity disk so that the original data can be rebuilt if something goes wrong. Used for large files, multimedia, etc.
RAID4: Block-level striping with dedicated parity. Like RAID3, but not commonly used.
RAID5: Very popular choice. Block-level striping with distributed parity. Both data and parity is distributed across all the drives in the array. Removes bottleneck of a dedicated parity disk. Probably best overall choice unless the environment is write-heavy.
RAID6: as RAID5, but dual distributed parity. This means that two sets of parity info are calculated - adds extra fault-tolerance.
