I have 4*2TB HDD drive in NAS. now the storage is full and i have planned to upgrade 2*10TB. Then how should i transfer exciting files to new 10TB hard drive.
Simply replace a drive and it will rebuild automatically. After replacing two drives you will see more capacity availableRAID calculator might be useful https://www.synology.com/en-uk/support/RAID_calculator?hdds=2%20TB|2%20TB|10%20TB|10%20TBI hope this helps.