Snapshots and growth
I have a question about snapshot growth and retention. Last week we had 14 days worth of snapshots and due to some storage growth, we changed this to 7 days worth of snapshots. Before the chan...
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For the 5 TB that we expected, we just added the snapshot sizes from days 8 thru 14.
Before the change, snapshots sizes where like this:
Most recent: 11 TB
Recent -1: 1 TB
Recent -2: 900 GB
Recent -3: 800 GB
and so on for a total of 21 TB
Now the data looks like this:
Most recent: 4.6 TB
Recent -1: 1 TB
Recent -2: 900 GB
Recent -3: 800 GB
and so on for a total of 10 TB
So you are telling me that there was 6 TB of shared and dedup data in the most recent snapshot that was reference in the snapshots from days 8 - 13?
I have reached out to our SE to see if he could insight into this.
Here is the response I got back from our SE
"The GUI shows the newest snapshot as larger than the others primarily due to how storage space is reported concerning snapshots. When a new snapshot is created, it initially captures the entire state of the volume at that moment. This means that the size displayed for the newest snapshot may appear larger because it incorporates shared data that has not yet been de-duplicated.
Here are the key points to understand:
- Baseline Snapshot: The largest snapshot in a group may contain baseline data not present in earlier snapshots. This is typical behavior, as newer snapshots represent the cumulative data differences since the last baseline was established.
- Family Shared Space: The newer snapshot is often reported to include "Family Shared Space," which is the amount of data shared across multiple snapshots. This shared data, which might not be reflected in the logical or unique space of earlier snapshots, can inflate the size of the newest snapshot displayed in the GUI.
- Snapshot Space Accounting: When a snapshot is taken, it initially has a size of zero (as it is an exact copy of the volume). As data changes between snapshots, space used increases based on the amount of unique data since the last snapshot.
- Data Reduction and Deduplication: The apparent discrepancy may also arise from data reduction and deduplication processes, which can lead to unusual space reporting in snapshots post-processing.
Thus, the relatively large size of the newest snapshot is a normal occurrence and reflects the complexities of space management in snapshot technology, particularly in regards to baseline data and space sharing among snapshots"
