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Why a RAID 5 Does Not Provide Perfect Data Protection

Arguably one of the most reliable forms of data storage, Raid-5 is not without fault and is far from perfect.


Most businesses use some type of RAID as a primary form of data protection. By definition, a RAID provides redundancy, meaning that no file exists in a single physical location; many types of RAID servers can sustain one, two or three hard drive failures without losing data.

RAID 5 is by far the most common RAID level for business web servers and storage servers. Unlike earlier versions of RAID, RAID 5 uses parity and block-level striping to write information. RAID 5 is cost efficient, fast and redundant, and when properly managed, a RAID 5 can run for years without losing data or experiencing serious downtime.

Contrary to popular belief, however, RAID on its own will not safeguard a business against data loss. All businesses need a secondary and tertiary method of data backup to prevent RAID data loss.

What Happens When RAID 5 Systems Fail

The main reason that a RAID 5 is not a perfect storage system is its rebuild process. When a hard drive fails, the RAID needs to replace that hard drive by drawing parity information from the other disks and its controller.

This is an intensive process that can take several hours under some circumstances. Until the rebuild is complete, the RAID does not provide redundant data storage. If a second hard drive fails, the RAID 5 will lose data.

The danger is that a second hard drive will fail due to the exceptional stress associated with the rebuild process. While most businesses execute RAID rebuilds regularly without issue, the chances of a drive failure are significantly higher during rebuilds than during standard operation.

Some businesses also attempt rebuilds after their RAID 5 systems experience logical failures or data corruption. This can lead to serious, permanent data loss if the rebuild overwrites critical files or causes a loss of parity information. Businesses should always approach logical RAID issues with the help of a qualified data recovery company in order to limit their chances of permanent data loss.

Finally, a RAID 5 might lose data if it shuts down unexpectedly before completing the rebuild process. Power failures and surges can quickly cripple a RAID 5, although this is not always the case depending on the RAID controller. We recommend using battery or generator backups when rebuilding important RAID systems as an extra precaution.

Decreasing the Chances of Data Loss Due to Hard Drive Failure

If your RAID array loses a member, you should inform your system administrator and immediately consider a rebuild if the RAID is in otherwise perfect working order. If you cannot access any files on the RAID, however, you should not attempt a rebuild. Doing so may overwrite key data and make data recovery difficult on your array.

Always keep a backup of important RAID data. Many businesses keep several backups, including archival copies, in order to prevent any data loss associated with a failed RAID 5 rebuild. If you can access your array after a hard drive failure, you might consider manually backing up the most important files on the array before attempting a rebuild.

Businesses should contact qualified data recovery companies when dealing with any type of RAID 5 data loss. At Secure Data Recovery Services, we have years of experience with all RAID levels, controller cards, configurations and file systems. Whether you need to recover files after consecutive hard drive failures or due to a logical issue, our customer service team is ready to discuss your case at 1-800-388-1266. Call today for a free RAID evaluation or for more information.

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