A snapshot is a full copy of a LUN in SAN storage.

In Huawei OceanStor systems, a snapshot is not a full physical copy of the data. Huawei uses a technology called HyperSnap, which typically employs a "Copy-on-Write" (COW) or "Redirect-on-Write" (ROW) mechanism.

When a snapshot is created, the system generates a point-in-time (PIT) logical image of the source LUN. It does not immediately duplicate the data blocks; instead, it records the state of the data at that specific moment. If data in the source LUN is subsequently modified, the original data is preserved (in COW) or new data is written to a new location (in ROW) to maintain the integrity of the snapshot. Because only the metadata and the changed blocks are managed, snapshots are created near-instantaneously and consume very little initial space.

A "full copy" would be referred to as aClone (HyperClone)or aLUN Copy, both of which require a 1:1 ratio of physical storage space relative to the source and take significant time to complete. Therefore, a snapshot is a virtual, point-in-time image, not a full physical duplicate.