Home > Storage > PowerScale (Isilon) > Product Documentation > Data Efficiency > Next-Generation Storage Efficiency with Dell PowerScale Inline Data Reduction > Inline deduplication efficiency estimation
A dry run Dedupe Assessment job is provided to help estimate the amount of space savings that will be seen on a dataset. Run against a specific directory or set of directories on a cluster, the deduplication assessment job reports a total potential space savings. The assessment job uses a separate configuration. It also does not require a product license and can be run before purchasing F910, F900, F810, F600, F200, F700/7000, H5600, and A300/3000 hardware to determine whether deduplication is appropriate for a particular dataset or environment.
The deduplication assessment job uses a separate index table to both inline deduplication and SmartDedupe. For efficiency, the assessment job also samples fewer candidate blocks and does not actually perform deduplication. Using the sampling and consolidation statistics, the job provides a report which estimates the total deduplication space savings in bytes.
The DedupeAssessment job can also be run from the OneFS command line (CLI):
# isi job jobs start DedupeAssessment
Alternatively, inline deduplication can be enabled in assessment mode:
# isi dedupe inline settings modify –mode assess
One the job has completed, review the following three metrics from each node:
# sysctl efs.sfm.inline_dedupe.stats.zero_block
# sysctl efs.sfm.inline_dedupe.stats.dedupe_block
# sysctl efs.sfm.inline_dedupe.stats.write_block
The formula to calculate the estimated deduplication rate from these statistics is:
dedupe_block / write_block * 100 = dedupe%
The deduplication assessment does not differentiate the case of a fresh run from the case where a previous SmartDedupe job has already performed some sharing on the files in that directory. We recommend that the user should run the assessment job once on a specific directory, since it does not provide incremental differences between instances of the job.