Specifications

NetApp Deduplication for FAS and V-Series Deployment and Implementation Guide
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Note: If Snapshot copies are turned off for the volume (or no copy exists in the volume) this is not a
recommended configuration or volume for deduplication.
Configuration B: LUN Configuration for Shared Volume Space Savings
If the user wants to apply the freed blocks to both the fractional overwrite reserve area and the volume free
pool, this can be accomplished with the following configuration:
1. LUN space reservation value = on
2. Volume fractional reserve value = any value from 1 – 99
3. Volume guarantee = volume
4. Snap reserve = 0%
5. Autodelete = off
6. Autosize = off
7. Try_first = volume_grow
Description: The only difference between this configuration and configuration A is that the amount of space
reserved for overwrite is based on the fractional reserve value set for the volume. As a result, this
configuration splits the free blocks between fractional overwrite reserve and volume free space. For
instance, if the fractional reserve value is set to 25, 25% of the freed blocks go into fractional overwrite
reserve and 75% of the freed blocks are returned to the volume free pool.
Pros and cons: The advantage of this configuration is that overwrite space reserve does not increase for
every block being deduplicated. Freed blocks are split between volume free pool and fractional reserve. The
disadvantage of this configuration is that overwrites to the LUN beyond the fractional reserve capacity may
fail because freed blocks may have been already allocated. Another disadvantage of this configuration is
that freed blocks stay in the parent volume and cannot be provisioned to any other volumes in the
aggregate.
Note: If Snapshot copies are turned off for the volume (or if no Snapshot copy exists in the volume) and
percentage of savings due to deduplication is less than the fractional reserve, then this is not a
recommended configuration or volume for deduplication.
Configuration C: LUN Configuration for Maximum Volume Space Savings
If the user wants to apply the freed blocks to the volume free pool, this can be accomplished with the
following configuration:
1. LUN space reservation value = on
2. Volume fractional reserve value = 0
3. Volume guarantee = volume
4. Snap reserve = 0%
5. Autodelete = off
6. Autosize = off
7. Try_first = volume_grow
Description: The only difference between this configuration and configuration B is that the value of
fractional reserve is set to zero. As a result, this configuration "forces" all the freed blocks to the volume free
pool and no blocks are set aside for fractional reserve.
Pros and cons: The advantage of this configuration is that all the freed blocks are returned to the volume
free pool. The disadvantage is that the chance of overwrite failure is higher than with configurations A and B
because no freed blocks are assigned to the fractional overwrite area.