Managing Snapshot(s)

A Snapshot captures the state of the data in a source Volume at a specific moment. It is used for backups or for restoring data later.

The size of a snapshot in block storage may not match the size shown in the file system. This is because the file system might not immediately mark unused blocks as free. As a result, the block storage system includes these blocks in the snapshot, even if they do not contain any data.

To reduce snapshot size and lower storage costs, you can 'trim' or 'discard' these unused blocks. This can be done by scheduling fstrim to run periodically or by mounting the Volume with the discard option, which informs the block storage system which blocks are in use and which are not.

size ของ Snapshot จะคำนวนจากการเปลี่ยนของข้อมูลเมื่อเทียบกับ Snapshot ก่อนหน้าของ Volume เดียวกัน ซึ่งอาจจะทำให้เกิดเหตุการณ์ที่ทำให้ Snapshot มีขนาดใหญ่กว่า Volume ได้

เช่น

The size of a snapshot is calculated based on the data that has changed since the previous snapshot of the same Volume. This can sometimes lead to a situation where a snapshot is larger than the Volume itself. For example:

The first snapshot of a 100 GB Volume containing 40 GB of data will result in a 40 GB snapshot.
Later, the data on the 100 GB Volume changes: 30 GB of the original data is deleted, and 80 GB of new data is written.
The next snapshot, taken when the 100 GB Volume now contains 90 GB of data, will result in a snapshot size of 110 GB. This is calculated from the two changes combined:
- 30 GB from the data that was deleted.
- 80 GB from the data that was added.