RAID 5 is one of the most popular RAID configurations offering performance advantages of a striped set with distributed parity. The RAID 5 configuration uses block-level striping with parity data distributed across all member disks. It has achieved popularity due to its low cost of redundancy. It also, provides faster data access speeds than RAID 4, a similar configuration with a dedicated parity drive. A RAID 5 can write to all of its hard drives simultaneously, whereas a system with a dedicated parity would be limited by the speed of the parity drive.


RAID 5 Failure Rate

The maximum number of drives in a RAID 5 configuration is theoretically unlimited. However, it is a common practice to limit the number of disks as the tradeoff of larger redundancy configurations is a greater probability of a simultaneous double disk failure, the increased time to rebuild a redundancy group, and the greater probability of encountering an unrecoverable sector during RAID reconstruction. As the number of disks in a RAID 5 group increases, the failure rate increases. RAID 6 is an alternative that provides dual parity protection thus enabling larger numbers of disks per RAID configuration.

The read performance of RAID 5 is almost as good as RAID 0 for the same number of disks. The distribution of data over the drives follows the same pattern as RAID 0 except for the parity blocks. Sometimes, in the event of a system failure while there are active writes, the parity of a stripe may become inconsistent with the data. If this inconsistency is not detected and repaired before a disk or block fails, data loss may result in a failed parity to be used to reconstruct the missing block in that stripe.

RAID 5 Recovery Process

Because the parity block information is distributed on the same disks used to hold striped data, it is written to a data disk that does not hold the striped data. Thus, a loss of a striped disk will not result in the loss of parity information and it can be used to recover the contents of the stripe. However, data loss can occur in the event of a second drive failure as the array is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive.

Many RAID 5 configurations can have recovered data from a failed drive and enable the replacement of physical disk drives while the array continues in operation. Hot swappable drives can be useful in RAID 5 systems because they can be changed out while the server is powered. However, most RAID 5 systems need to be rebuilt after losing a hard drive as it might be masked from the end-user and we highly recommend to contact a professional data recovery company to avoid permanent data loss.

We provide unmatched data recovery and digital discovery services for all types of high-capacity storage devices including redundant arrays of independent disks (RAID), storage area networks (SAN), network attached storage (NAS) and other types of multi-drive server configurations. Data Recovery Labs have extensive experience with RAID 5 data recovery process and developed custom tools and techniques to achieve industry-leading recovery rates.

Recommended Applications For RAID 5 Arrays

  • File and print servers
  • Relational databases
  • Transaction processing
  • Web, email, and news servers
  • Intranet servers

RAID 5 Failure Case Scenarios

How To Best Handle RAID Failure

If any of your RAID disks indicate any signs of hardware damage – potentially, making mechanical noises – make sure to act quickly to prevent potential permanent data loss. First, shut down the RAID and do not make any attempt to repair damaged hard drives by running CHKDSK or any other repair utilities or defragmenter utilities. These tools can exacerbate data loss issues of your array, greatly reducing the chances of a successful recovery. Keep the RAID powered off and contact a quality data recovery specialist.

If for any reason, you decide to attempt recovering the drive(s) yourself, first make sure to label the drives with their position in a RAID array. Do not replace a failed drive with a drive that was part of another RAID system and make sure to zero out the replacement drive before using.

Data Recovery Labs does not recommend any commercial data recovery software for RAID 5. Many commercial programs can decrease the chances of a successful data recovery by overwriting corrupted data. If your RAID 5 has mechanically damaged hard drives, running any type of software can cause permanent file loss.