Many of our clients mistakenly believe that their RAID arrays are error proof. In reality there is no such thing as a perfectly dependable server or storage system, and while RAID 5 systems offer excellent speed and reliability, they are not a suitable substitute for a good backup strategy.
Simultaneous Hard Drive Failures
One of the defining features of RAID 5 is its fault tolerance, but when a RAID member is physically damaged, the entire array has a single point of failure. Another hard drive failure will render the array unreadable.
Simultaneous hard drive failures are not necessarily a rare occurrence. Rebuilding a RAID 5 puts tremendous stress on the remaining disks, increasing the chances of an actuator head crash or another mechanical issue. Some businesses try to prevent this by creating a backup before rebuilding, but this practice also puts stress on the other hard drives.
The best way to safely replace a damaged RAID drive is to have a backup on hand in case the array requires several simultaneous replacements. Most businesses will never deal with multiple drive failures, but a little bit of early preparation can prevent a large-scale data disaster.
Controller Card Issues
Problems with your RAID's controller card can cause parity loss, particularly during rebuilds. Your array might also stop working suddenly, but a failed controller card will not necessarily prevent you from accessing your files depending on the extent of the damage. You will typically notice slow performance immediately, and if your array has parity issues, you will not be able to successfully rebuild the system after a hard drive failure.
Accessing your RAID with a different controller can be difficult depending on the model of your card and the complexity of your configuration. To treat controller card issues, data recovery engineers need to use a case-specific approach to create a safe, simulated copy of each array.
While most RAID systems have safeguards to protect data while new members are integrated, arrays are inherently sensitive during rebuilds. If a sudden power outage or other event causes the rebuild to fail, the array may lose critically important parity information. This will prevent subsequent rebuilds from finishing successfully.
Never attempt a second rebuild when an initial attempt fails. Keep the system powered off until you can get a professional evaluation from a data recovery provider.
Accidental file deletion, formats, virus infection and other preventable sources of logical damage comprise a major percentage of data loss scenarios. Hundreds of RAID systems are accidentally reinitialized or formatted each year, and businesses rarely have a full backup.
Avoiding Data Loss on a RAID 5
Of course, the best way to avoid data loss is to back up your RAID 5 regularly. Remember, any storage device or array can fail, and multiple backups are the only way to completely protect important system.
While most RAID arrays are completely recoverable with the right tools and expertise, you will drastically improve your chances of a successful recovery by turning your system off as soon as possible after the failure. Do not attempt to rebuild or reinitialize your array.
At Secure Data Recovery Services, we treat hundreds of RAID systems each year. While RAID 5 failures are fairly uncommon, they are typically treatable when the array is shut down quickly. If your RAID 5 fails and you cannot rebuild the array for any reason, our free diagnostics provide a great way to assess recovery options while minimizing your system downtime.