What is RAID?
RAID (Redundant Array of Independent Disks) is a storage technology that combines multiple physical hard drives into one unit for the purpose of data redundancy, speed, or a combination of the two. There are many different types of RAID, called levels, and written as a number after “RAID” (eg. RAID 0).
It is a surprisingly common belief that a RAID designed for redundancy should not fail, but this is not the case. In reality, RAID can fail in several ways. A malfunction in the controller, multiple disk failure, a power surge, accidental data deletion, ransomware attacks, rebuild errors, and wrong replacements of good disk elements are the usual failures experienced with RAID servers.
Is RAID-5 safe?
RAID 5 is a RAID level that has become a large topic of discussion. With RAID 5, data is spread across the drives (striping) and an error protection scheme (single-parity) is employed. While this may seem good on the surface, RAID 5, many people advise against using RAID 5 as it only protects against a single drive failure. It relies on all other drives in the array to be working in order to fully reconstruct lost data from the first failed drive. Moreover, given that higher and higher capacity HDDs are being used within RAID arrays, the likelihood of failure increases, based on the increased likelihood of bad sectors to be found in larger disk volumes.
What to do if you experience a RAID failure?
It is essential that the RAID array is powered off, and no attempt is made to replace disks, or ‘force’ disk back online. This can result in a ‘bad rebuild’ whereby incorrect data is written through the volume. Doing so can cause irretrievable data loss. Please contact CDR if you require professional assistance with the recovery of data.