After OceanStor 9000 is configured with InfoStamper snapshot, which of the following description of data snapshot is correct? (Multiple choice)

Question

Options

• AAfter a snapshot is deleted, the snapshot data unique to the snapshot will be cleared, and the data
• BAccess to snapshots. Read snapshot data that is smaller than the snapshot number. The snapshot
• CAfter creating a snapshot, the write operation of the data shard will trigger the data to be written to
• DWhen creating a snapshot, the data layer does not change, but the reading and writing of data will

• A
  78% (38)
• B
  22% (11)

Explanation

Options A, C, and D correctly describe how OceanStor 9000's InfoStamper snapshot technology works using a Copy-on-Write (CoW) mechanism. When a snapshot is created, no data is physically copied immediately - the data layer remains unchanged (D), meaning snapshot creation is fast and non-disruptive, though subsequent I/O operations carry slight overhead due to CoW tracking. Once a write occurs to an original data shard after a snapshot exists, the original data is first preserved to the snapshot space before the new data is written (C) - this is the CoW trigger in action. When a snapshot is deleted, only data blocks exclusively owned by that snapshot are freed; blocks shared with other snapshots or the active filesystem are preserved (A), ensuring data integrity across the snapshot chain.

Option B is incorrect because it misrepresents snapshot read access - data access is not restricted or ordered by snapshot number in the way implied; each snapshot independently captures the filesystem state at its creation point and can be read without such constraints.

Memory tip: Think of InfoStamper snapshots like a "freeze-and-branch" model - creation freezes the pointer (no data moves), writes branch the data (CoW triggers a copy), and deletions only reclaim what no one else shares. The acronym C-W-D (Create=no change, Write=triggers copy, Delete=clears unique data) maps directly to D, C, and A respectively.

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