RAID 1 (Mirror) – Helps protect data

A RAID 1 configuration has  a minimum of two disks in the array. However, more can added. The RAID 1 configuration is referred to as a ‘mirror’ as any data written to a disk is duplicated on the other disks in the RAID 1 set. If one disk fails in the RAID 1 the computer user should be notified, and the failed disk should be replaced with a new disk. The RAID 1 will then rebuild by synchronising the data from the remaining good disk(s) to the new disk.

As the capacities of HDDs have increase the popularity of RAID 1 versus RAID 0 or RAID 5 has increased. RAID 1 configuration is also easy to maintain for the system administrator. It is possible that individual disks can be removed from the RAID 1 and plugged into a separate computer, and the data can be accessed directly. This is not the case for other RAID configurations.

RAID 1 increases the read speed of files, but write speed is the same as a single disk configuration.

RAID 1 configuration diagram

Why would you require recovery of a RAID 1 array?

Whilst RAID 1 arrays provide increased reliability and easy management we still find they require recovery. The reasons for is are as follows:

  • Multiple disk failure. Sometimes this occurs at the same time (e.g. due to physical shock, liquid damage etc.) However, more frequently we find that one disk in the RAID 1 array has failed some days, weeks, or even months before the second disk failure. The failure of the first disk went unnoticed, or even ignored, by the customer. Then the second disk failed and data loss occurs. Often it is necessary to process both disks to ensure that the ‘up-to-date’ version of the data is recovered.
  • Corruption of the filesystem. If incorrect data is written to a  RAID 1 array, then the data shall be written to all disks in the RAID set. Typical failure related to corruption of the meta data which creates the folder and file name structure (e.g. Master File Table, Catalog, or iNode structures).
  • User error. If a device is formatted or file are  deleted then all disks in the RAID 1 will be affected.

What services can CDR provide?

  • Recover your lost data.
  • Provide a disk image to allow an attempt to make the computer / server bootable.
  • Advise on appropriate backup method.
  • Provide a fixed price quotation in advance of receipt of any RAID array.
  • Experienced staff with technical expertise can talk you through the process, including any early stage diagnosis before the RAID is received.
  • Please phone 0161 408 4857 to discuss your data recovery.