RAID 1 is a Redundant Array of Inexpensive disks that uses a data management format known as Mirroring. A mirror is an exact replica of a piece of data created on one or more volume. This data is then stored as a “mirror-image” on the number of disks that are aligned in this configuration.
The Right Configuration for the Job?
RAID 1 provides a maximum level of data redundancy, but it does not include as many appreciable speed increases to a system as you would find in a RAID 0 array. Instead, RAID 1 is the choice of the user who above all needs to have safe copies of their data at hand and protected from the errors and failures of a hard drive.
In terms of speed, once a RAID 1 array is set-up, it is possible for a computer to read two different portions of the same data at the same time, which would in theory double the existing speed of the system in a data management term known as duplexing.
This speed boost is highly contingent on the manner of hard disk used, as well as the RAID controller involved in the situation. An older IDE configuration can still only read a single disk at a time in trying to access information. Therefore, RAID 1 is a slower alternative with these older drives.
A RAID 1 array can only be as big as the smallest disk in the configuration. If you were to array two hard disks, one of 100GB and another of 250GB, your overall RAID array would then be 200GB in size, with 150GB of hard drive space still free.
The biggest disadvantage of RAID 1 is that it effectively halves the possible storage space one would have on their computer. Instead of having two 250GB hard disks, used independently for 500GB of space, you would have effectively half of that to fill with data. The other half is dedicated to maintaining a mirror of that data instead of additional space for storage.
The Stability of RAID 1 Arrays
Reliability is quite high if you were to assume that a hard disk would be replaced in the event of a failure or malfunction. Assuming this, there is a .0004 percent chance that both drives will fail and your data would be lost in its entirety. Breaking these kinds of mirrors would be several years of bad luck indeed at that level of reliability, but assuming your disks have an adequate RAID controller and are arrayed correctly, you should be quite safe from the aggravating black hole of data loss.
Still the administrative advantages of RAID 1 make it a popular option for those looking to keep the integrity of their data intact at all times. A mirror can be split, allowing one disk to be removed and backed up or replaced, and the system will not miss a beat. Instead it will continue to function normally, and then when the hard disk is reactivated or reinstalled after a failure, rebuilding the mirror requires minimal effort.