Data recovery from redundant complex data storages

Most complex data storage systems ensure data safety by means of redundant recording distinguished by three types: mirroring (providing for an exact extra copy of data), parity (application of data conversion allowing to achieve redundancy) and redundancy based on parity and GF-algebra method.

Mirroring
Mirroring method is applied in RAID level 1 and its combinations with other data distribution methods. With this method several RAID-components contain the same information. Data can be recovered from any copy.

Parity
This method is applied to RAID levels 3, 4, 5 and 7. Data can be recovered if only one of the components fails. Generally, to recover information lost from such RAID-systems it's necessary to use data from all other components and parities. This RAID differs in algorithm of data distribution across the components. RAID 3, 4 and 7 employ separate components to store parity and the data are evenly distributed across the rest of the components. In RAID level 5 the data and parity are evenly distributed across all components. When recovering data from these systems, you should take into account data distribution algorithm and quantity of active components. If more than one component fails data recovery is possible only after the components are repaired. It's not recommended to conduct this operation by yourself and rather take the device to a specialized service center.

Reed-Solomon code (redundancy based on parity and GF-algebra)
This method is introduced in RAID level 6. It provides for a possibility to recover lost information even after failure of two components. This is a hybrid system which uses two algorithms to ensure redundancy. If one component fails data can be recovered in the same way as from RAID5 using data from other components and parity. The second redundancy algorithm allows to recover lost data if one more component fails.

Even data distribution across all the components of RAID-systems level 3, 4, 5, 6, 7 makes impossible to recover lost information from a separate component. Before starting data recovery from a RAID-system components assembly is required. UFS Explorer allows to virtually assemble these RAID levels imitating data distribution algorithm applied by controller of the given massive and thus reading information on the file system as it is. If components of these arrays fail UFS Explorer enables data recovery using redundant information.