How can I restore files lost from RAID?
Multiple disk units known as RAID are widely employed in both home and office environments thanks to their high capacity, increased speed and, of course, resilience to disk failures. In fact, such systems have proved to be quite dependable, yet, under certain circumstances things may still go awry: faulty rebuild operations, errors of the RAID controller or software emulator, failed upgrades, server crashes or accidental deletion and formatting pose a threat to the integrity of data stored within the array and may even result in the total loss of files.
Earlier, data recovery from RAID could not be accomplished without professional assistance. Fortunately, nowadays modern techniques allow processing such systems just with a single piece of software – provided that the unit remains functional (at the very least in the degraded mode). However, improper steps taken during the procedure may cause secondary damage to the missing information and make it irretrievable. Therefore, before getting down to it, make sure that you avoid the following operations:
- Having connected the drives to the computer for data recovery, don't mount your RAID in the read-write mode to prevent data overwriting;
- Don't try to rebuild the array as this operation may create a new RAID with the default settings which will overwrite the older configuration. Moreover, this process increases the load on the system and may lead to the failure of one of the drives;
- Don't keep running the storage in the degraded mode as another disk failure will make it problematic or even impossible to recover the lost data;
- Don't attempt to repair the system or replace the failed disk until you are sure that all of the important data is recovered or backup copies of the member disks are created;
- The procedure of full format, the TRIM command on solid-state drives and other writing operations performed either by the system or by you imply permanent wiping of the data deleted or lost from RAID.
Data in RAID is not simply spread across multiple disks but allocated in accordance with the chosen distribution algorithm. In view of this, RAID recovery suggests the reconstruction of the array and subsequent search for deleted or lost files.
There are several types of RAID and each configuration has its own characteristics that determine the peculiarities of the data recovery procedure and impact the probability of its successful outcome. In order to find out how you can get your files back, please, choose the type of the utilized complex storage system:
- Systems with redundancy include such configurations as RAID 1, RAID 3, RAID 4, RAID 5, RAID 6, etc.;
- Systems without redundancy are represented by RAID 0 and JBOD;
- Complex combined systems incorporate such layouts as RAID 0+1, RAID 10, RAID 50, RAID 50E, RAID 60, etc.
- Distributed SAN systems usually employ disk arrays implementing one or several of the above-mentioned RAID levels that are presented as network block devices through Fibre Channel, iSCSI or AoE protocols.
Last update: January 23, 2020