NetApp SnapShot uses copy-on-write technology. However, there would be difference in the case of if SnapReserve is enabled or not.
If SR is not enabled, then there will be no data copies at all (so, not copy-on-write strictly speaking), because new data will always be written to new and empty blocks.
If SR is enabled, then copying will happen, and blocks will be written to the reserved area before writes, which will also have a performance hit, because the change will be waiting on writes.
Am I understanding this correctly?
Thanks!