What Is RAID 1?

RAID 1 is a configuration of a mirrored set without parity. A RAID 1 creates an exact copy (or mirror) of a set of data on two or more disks. This is useful for applications where read performance and reliability are more important than data storage capacity. RAID 1 capacity is limited by the size of the smallest member disk.


Known as "Disk Mirroring" RAID 1 is comprised of two disks (view diagram above), which increases reliability geometrically over a single disk. Failure rate of a classic RAID 1 with two identical models of a disk drive is extremely low which makes it a highly dependable option, as the system will not lose data as long as one drive is functional. RAID 1 represents an inexpensive and convenient way of providing data redundancy and makes it a rather common choice for smaller servers and home desktops.

This configuration, however, does not offer performance improvements over a standard hard drive and may actually hinder performance without the implementation of multiple RAID controllers. Because of this, RAID 1 is usually used when high fault tolerance is more critical than overall performance.

While RAID 1 provides significant protection, no RAID configuration perfectly prevents data loss. Since each member contains a complete copy of the data, and can be addressed independently, ordinary wear-and-tear reliability can be significantly increased simply by adding self-contained copies. Thus many users often choose to mirror RAID 0 or RAID 5 arrays with a RAID 1, creating an identical copy of the primary array to add additional redundancy.


In general RAID 1 recovery success rates are pretty high due to the primary advantage of this array having one write, two reads possible per mirrored pair. The quality and integrity of the recovered data, however, will depend on the extent of the damage incurred to each failed storage device. If the mirrored disk was working correctly up to the point of failure, then there should be identical copies of the data on at least two drives which will provide two chances to recover the same data. The high level of redundancy of data means we do not have to rebuild it in case of a disk failure but will need a copy of the replacement disk.

Typically the RAID function is done by system software, loading the CPU / Server and possibly degrading throughput at the high activity levels, however hardware addition to configuration is strongly recommended. Although generally a good solution for data protection we nonetheless, receive RAID 1 arrays with bad mirrors, corrupted data being duplicated on to the other drive, incorrect rebuild, as well as failure to boot into the operating system. Data Recovery Labs engineers have extensive experience with RAID 1 arrays and developed custom tools for successful recovery. Continuous developments in our R&D initiatives ensure that we have the very latest techniques and technology to allow us to live up to our reputation in the industry. Please visit our Testimonials page for more information on RAID recovery cases.

Recommended Applications For RAID 1 Arrays

  • Databases
  • Small servers / home computers
  • Applications requiring very high reliability
  • Applications not requiring very high performance

Most Common RAID 1 Failure Reasons