Trident backend option 'snapshotReserve' creates larger ONTAP volumes than expected
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- 239
- Visibility:
- Public
- Votes:
- 0
- Category:
- trident-kubernetes
- Specialty:
- snapx
- Last Updated:
- 11/22/2023, 5:00:28 PM
Applies to
Astra Trident 21.07 and higher
Issue
- When defining an ONTAP Trident backend to provide PVCs that also have snapshot capability, or where the volumes will run ONTAP based snapshots, a
snapshotReservecan be set for every PVC under the defaults section of the backend. - When a PVC is requested with a certain size, the amount of space assigned to snapshot usage (and therefore total volume size) appears to be larger than expected if adding the
snapshotReservepercentage to the requested PVC size [Total volume size = (PVC requested size) * (1 + (snapshotReserve percentage) / 100)] - Below is an example of the resulting volume size in ONTAP for a PVC specifying a 1GB volume based on different
snapshotReservepercentages specified in theontap-nas backend[setting asnapshotReserveof 100% is not possible (#DIV/0)]:
|
PVC |
PVC snapshotReserve % Percentage |
ONTAP snapshot-reserve-available (GB) |
ONTAP Total Volume Size(GB) |
| 1 | 10 | 0.11 | 1.11 |
| 1 | 20 | 0.25 | 1.25 |
| 1 | 30 | 0.43 | 1.43 |
| 1 | 40 | 0.67 | 1.67 |
| 1 | 50 | 1 | 2 |
| 1 | 60 | 1.5 | 2.5 |
| 1 | 70 | 2.33 | 3.33 |
| 1 | 80 | 4 | 5 |
| 1 | 90 | 9 | 10 |
| 1 | 100 | #DIV/0! | #DIV/0! |
