OS5 X64 BTRFS snapshot guide:

Snapshot_OS5_x64_v2.pdf

Each model would keep difference snapshot copy depend on NAS’default DRAM size, and then new copy would replace oldest.

2GB -> 64
4GB -> 128
8GB-> 256
16GB -> 512

Example
N2810 2GB DRAM -> 64
N2810 PLUS/PRO 4GB DRAM -> 128
N4810 4GB DRAM -> 128
N5550 2GB DRAM -> 64
N5810(PRO) 4GB DRAM -> 128
N8900PRO 8GB DRAM ->256
N16850 16GB DRAM ->512
N16910SAS 16GB DRAM ->512