Administrator Guide

• Data compression – Uses algorithms to reduce the size of stored data.
When using data reduction, note the following limitations:
• The minimum le size to be considered for data reduction processing is 65 KB.
• Because quotas are based on logical rather than physical space consumption, data reduction does not aect quota calculations.
• If you disable data reduction, data remains in its reduced state during subsequent read operations by default. You have the option
to enable rehydrate-on-read when disabling data reduction, which causes a rehydration (the reversal of data reduction) of data
on subsequent read operations. You cannot rehydrate an entire NAS volume in the background, although you could accomplish
this task by reading the entire NAS volume.
• Cross-volume deduplication is not supported at this time.
• Data reduction does not support base clone and cloned volumes.
Table 16. Data Reduction Enhancements in FluidFS v6.0
FluidFS v6.0 or later FluidFS v5.0 or earlier
Data reduction is enabled on a per-NAS-cluster basis. Data reduction is enabled on a per-NAS-volume basis.
Data reduction supports deduplication of les that are created
or reside on dierent domains.
Data reduction is applied per NAS controller, that is, the same
chunks of data that are owned by the dierent NAS controllers
are not considered duplicates.
The distributed dictionary service detects when it reaches
almost full capacity and doubles in size (depending on available
system storage).
The dictionary size is static and limits the amount of unique data
referenced by the optimization engine.
Date Reduction Age-Based Policies and Archive Mode
By default, data reduction is applied only to les that have not been accessed or modied for 30 days to minimize the impact of data
reduction processing on performance. The number of days after which data reduction is applied to les is congurable using Storage
Manager.
The default number of days is set to 30. When using FluidFS v5 or earlier, you can change the default to as low as 5 days, and you
can start data reduction processing immediately (archive mode). Starting with FluidFS v6, there is no archive mode available. You can
set the Exclude Files Accessed in the Last and Exclude Files Modied in the Last defaults to 1 day instead of using archive mode.
For more information about enabling and disabling archive mode, see the Dell FluidFS FS8600 Appliance CLI Reference Guide.
Data Reduction Considerations
Consider the following factors when enabling data reduction:
• Data reduction processing has a 5-20% impact on the performance of read operations on reduced data. It does not have any
impact on write operations or read operations on normal data.
• Storage Center data progression is impacted. After data reduction processing, the Storage Centermigrate reduced data up to
Tier 1 disks.
• Increased internal trac during data reduction processing.
• Data is rehydrated for antivirus scanning.
• Data is rehydrated before being replicated to a target NAS volume. If replication is already congured, the data being reduced
was already replicated
• You cannot enable data reduction on a clone NAS volume.
• Data reduction stops automatically when a NAS volume has less than 5 GB of unused space. Therefore, a NAS volume resize can
inadvertently stop data reduction.
FluidFS NAS Volumes, Shares, and Exports
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