RAID 5 is a type of Redundant Array of Inexpensive Disks in which a computer uses block-level striping. This means that data is written in blocks on each of the drives on the array. This leaves parity data across all of the disks so as to be able to rebuild any missing sectors of a file in the event that one of the hard drives were to fail or break.
RAID 5 is usually achieved through hardware, such as a high-quality RAID controller. However, with Windows Operating Systems and Linux, they can enact software based controllers to monitor this configuration.
The Data on a RAID 5 array is written in parity stripes, which are then distributed across the drives in the array. These stripes of data are not read every time the hard drive performs a data read, but instead read when a system check finds what is called a cyclic redundancy check error, indicating a failure of the data distribution at some point in the array.
The Affordable Means of High-Level Redundancy
RAID 5 is advantageous to other forms of RAID for its affordable-cost redundancy, which would allow a user to create backups of all their information without sacrificing an entire disk to back up the data of another entire disk.
Four 500GB disks in a RAID 1 configuration for example would ultimately yield 1000GB of space to be filled with data, and 1000GB dedicated to mirroring that data. On a RAID 5 system, that same amount of hard disk space would become 1500GB of usable space instead.
Factors to Consider When Building a RAID array
Although in the grand scheme of things a RAID 5 system is affordable, it is not without cost. At a minimum of three disks, this will be a more costly solution. With that said, although the cost will justify itself in usable space and excellent reliability, it is still a factor for today’s user to consider. It is possible to use a “degraded” RAID 5 array, in which 3 disks exist on the drive, yet one of them is typically inactive until failure or need for backup. However, this would compromise the parity data’s integrity, and thus, the system’s overall reliability.
The parity data can then be used to reconstruct the error and fix the data issue without the main computer ever being the wiser as to what kind of error might exist. If a drive fails, the disks will then reconfigure their data in such a way as to reconstruct the missing pieces from parity files.
When the computer is rebuilding files in case of a failed drive, this is known as Data Recovery Mode. Again, the computer will recognize the failure and prompt the user to take action to recreate the integrity of the RAID array. This failure will not cause the system or programs to run unstably or to cause the system’s performance to plummet, operation will continue at more or less a normal level.
A RAID 5 Tip
Several RAID enthusiasts will always suggest that a user never use hard disks from the same production lot, thus decreasing the odds that a mechanical failure or compromised assembly will strike down all of your hard disks.