Redundant arrays of independent disks, or simply RAIDs, are becoming increasingly commonplace. Originally developed exclusively for the server market as a cost-efficient storage solution, for years RAIDs have been quite expensive and hard to implement, thus, restricted to business use only. Nowadays, this technology has become within the reach of any tech-savvy PC user. More and more households make use of NAS units, which typically have two or more hard disks organized into a RAID system, as a central storage area for their photo, music, video collections and file backups. Moreover, the processing power of modern standard computer systems allows anyone to build such an array with several hard disks and a RAID controller, or even choose a software RAID, which doesn’t require any additional hardware components. RAIDs are ideal for those who want to get crazyfast disk performance, better fault tolerance or increased storage capacity. However, although in comparison to a single hard drive a RAID offers much higher protection against data loss, it isn’t a panacea for all storage ills – there are still a lot of things that can go wrong, and when they actually do, you may find yourself in a tight corner. As a rule, RAID data loss disasters are caused by:
Apparently, like any digital storage medium, a RAID may suffer from data loss owing to some human mistakes, the most frequent of which are accidental deletion and formatting. Fortunately, as long as you haven’t written any new data to your RAID, the mistakenly deleted files can be easily restored, but once they get overwritten, there is nothing you can do to rescue them.
Typically, a RAID is made up by multiple hard drives and a controller, which manages all of them in a single system. As you know, hard drives are fragile and any physical damage or other kind of misuse may cause them to fail. Though the array is able to survive the failure of a single disk, running it in the degraded mode significantly increases the chances that the whole system will break down, taking your important files to a silicon grave. On top of that, power surges or other problems may result in the failure of the controller, making you unable to access the drives as well as all the data stored on them. Simple replacement of a controller will not fix the problem, as the configuration possibly won’t remain intact, and may make matters even worse.
Improper or failed RAID rebuild
Most common RAID types can still function when one of their drives fails, but the defective drive should be replaced as soon as possible and the entire array is to be rebuilt to get accessible again. However, sometimes this process is not carried out correctly, or unexpected hardware/software issues hinder an accurate rebuild. First of all, mechanical stress, heat or a sudden power outage can prompt an additional drive failure. What’s more, a user may accidentally run a rebuild with a missing or faulty hard drive, or choose an improper drive order or configuration. The failure of a RAID during its rebuild may have unpredictable consequences and even cause permanent data loss by overwriting all the data on the healthy hard drives.
Indeed, fault tolerance can sometimes manage to protect RAID’s data in case of a physical failure, but what about logical ones? Similar to a non-RAID hard drive, an improper system shutdown or drive ejection may wreak havoc with RAID’s file system, making the data stored on it inaccessible. Among other issues that can corrupt the file system are virus infections, software crashes and freezes, a damaged Master Boot Record, RAID configuration errors, a corrupted Master File Table, a missing RAID partition and many others. If you happened to face such a corrupted file system dilemma, don’t panic just yet. Provided that all of the hard disk drives that make up the RAID are functioning properly, a special data recovery tool will help you to retrieve the lost files.
The failure of a host server for any reason can render your RAID inaccessible. Moreover, a common situation is when a server crash occurs, to return its functionality the technical support may suggest some fixes that will put your data in danger and may even lead to the loss of all the files stored. Of course, it is advisable to refrain from using methods you’re not sure of, but if you’ve already let that happen, quality data recovery software is likely to save the day and bring the lost files back.
In fact, earlier, when users faced data loss from a RAID system, they had no choice but seek professional help and pay a small fortune for the recovery. Nowadays, with modern data recovery techniques, in most cases this process can be carried out using a single data recovery utility downloaded from the Internet. Still, you should remember that any erroneous operations may double the trouble bringing secondary damage to the lost data and result in its permanent loss, as even the most professional recovery experts can do nothing once the files are overwritten. To avoid this, having experienced a RAID failure, you should take the right steps to keep your data alive:
- First of all, turn your RAID off immediately. The more you run it in the degraded mode, the more likely you are to cause its further damage. Also, do not create, delete and move any files or continue to run any programs until you are sure that the important data is recovered. Furthermore, you shouldn’t try to rebuild the array (the missing data won’t magically appear after a rebuild) or use any file system repair and defragmentation tools as they may make the problem worse.
- Don’t attempt to repair the system yourself. In case of the physical damage of at least one drive in your RAID0 or JBOD, two drives in RAID3, RAID4, RAID5, RAID7 and more than two drives in RAID6, contact a data recovery specialist who has the needed tools and expertise to retrieve your files. An amateur hour can do irreparable damage to the affected disks and permanently erase your data. If possible, make notes of the events that preceded the failure to simplify the repair process and improve the chances of successful recovery.
- In all other cases, you can restore your files using data recovery software with the RAID support. Choose only those tools, whose developers explicitly state that their product operates in a safe read-only mode and won’t do any harm to the lost data trying to fix the corrupted structutres. Install the program onto your PC or Mac and run it. After that, you can attach the problem RAID to the computer (never try to to plug in individual RAID drives separately), specify its level, the order of drives and other parameters, and let the program virtually reconstruct your system, finding all the files that can be recovered. Having finished the recovery operation, you can save the image of your RAID to a safe location and load it to a data recovery software for further analysis.
On the whole, though RAID systems are quite complex and are to be handled with special attention, it doesn’t necessarily mean that the data lost from such an array has fallen off the face of the earth. For the most part you can recover it yourself by using special data recovery software. Yet, you should keep in mind that any of the mentioned errors may result in the severe damage of your files.