A redundant array of independent disks, or RAID, is a type of data storage virtualization that takes a configuration of multiple disk drives presented together as a single storage area where data can be written and read. It is a popular method of managing data storage and access because it tends to be faster, more stable and, better able to protect data in the event of drive failure.
RAID often provides data redundancy by storing information on multiple disks, meaning that users can still access data if one or two of the disks fail. The amount of redundancy and the ease of data recovery depends on the type of RAID being used. Though RAID does provide more stability and reliability, it can still fail from time to time. Depending on the type of failure, RAID recovery is often possible with professional help.
Types of RAID
There a number of configurations offered by RAID, but some of the most commonly uses include RAID0, RAID1, and RAID5. RAID0 is all about speed, but it doesn’t actually provide redundancy because it doesn’t duplicate information on multiple disks. Instead, RAID0 spreads single copies of information across multiple disks to allow faster read and write speeds. If a disk fails with RAID0, the data probably can’t be recovered without professional help.
RAID1 provides redundancy, though not as much speed. It relies on a pair of disks, onto which the duplicate data is written. If one drive fails, the other will keep working and allowing all data to be accessed until the other drive is replaced. If users want both speed and redundancy, the usually step up to RAID5.
RAID5 uses three or more disks and a method called parity data to provide faster speeds along with redundant data. Any drive can experience a failure and all the rest will continue to work. Data redundancy often causes users to neglect their backups because they feel they are protected, but complete failure can still occur and require RAID recovery.
Common causes of RAID failure
RAID can fail for a variety of reasons, though some are witnessed more often than others. Two common reasons why RAID will fail include multiple disk failure and controller failure. Multiple disk failure means that more than one disk in the array goes bad. RAID is protection against the failure of a single disk in the system, but the array is not intended to operate that way for long. Continuing with a failed disk can make the rest of the array more vulnerable to damage. If more than one disk fails, the entire system will break down.
RAID Controller failure is a bit different. While a RAID server has multiple disks, it usually operates using only one controller. If the controller fails, the system may encounter a variety of problems until it is replaced, including a struggle to boot. No matter what caused the failure in the RAID configuration, it’s a smart idea to consult with a data recovery expert to ensure that everything is still there. Attempting to fix or find anything without the proper tools and knowledge can result in permanent data loss, which is an even more disastrous problem than the initial failure.
What to do when RAID fails
The first thing to do when RAID stops working or begins to act up is to seek help from professionals. If a single disk fails, then it should be replaced as soon as possible before using the system to read or write more data. Many users are tempted to keep going with a bad disk to avoid downtime or lost business. Working with a bad disk is possible, but it means inviting the danger of further failure, making RAID recovery necessary.
Waiting for the disk to be replaced before further use can help users avoid data recovery entirely. However, if more than one disk fails, recovery help will be necessary. The best way is to turn the system off completely until help can be obtained. Users can help RAID recovery experts by making detailed notes about the failure to help them determine what caused it and how it can be fixed.
RAID failure does not necessarily mean data loss. If the right measures are taken in the right amount of time, then data can often be recovered by experts. A RAID recovery service can evaluate the hardware and determine whether and how data can be recovered.