In the original configuration the RAID-6 over the 6 disks was build using two different SATA controllers. Four disks were connected to RocketRAID and the other two connected to the integrated Intel SATA.
Now, the motherboard has changed to a new one with 6 SATA connections via the integrated controller. However, it caused tat the CPU and RAM were changed as well. So from the original configuration only chassis, PSU and the SATA disks left.
64-bit version of the same OS was installed.
Everything is working fine now.
Hashes are all OK.