Constant freezing of the system led to mainboard and hard disk replacement. The backup was a simple disk images by means of dd. After replacement the backup wouldn't work. It turned out that the BIOS stores some information about the RAID mode in the MBR. So the path to restored data is the following:

1. Install the new hard drive and make all necessary changes in the BIOS (JBOD/RAID0).
2. Restoring everything but the first sector.
3. Generate a new partition table from scratch rather than replacing the whole MBR.