Dell Storage Manager 2020 R1 Administrator's Guide

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NAS Volumes Storage Space Terminology

Dell Storage Manager displays storage space details for individual NAS volumes and for all NAS volumes collectively. The following table defines terminology used in Dell Storage Manager related to NAS volume storage space.


Term	Description
Size	Maximum size of a NAS volume defined by the storage administrator
Used space	Storage space occupied by writes to the NAS volume (user data and snapshots)
Reserved space	A portion of a thin-provisioned NAS volume that is dedicated to the NAS volume (no other volumes can take the space). The amount of reserved space is specified by the storage administrator. Reserved space is used before unreserved space.
Unreserved space	A portion of a thin-provisioned NAS volume that is not reserved (other volumes can take the space). To calculate the amount of unreserved space for a NAS volume, use: (NAS volume size) – (NAS volume reserved space)
Unused space	Storage space that is physically currently available for the NAS volume. To calculate the amount of available space for a NAS volume, use: (unused NAS volume reserved space) + (NAS volume unreserved space
Overcommitted space	Storage space allotted to a thin-provisioned volume over and above the actually available physical capacity of the NAS pool. To calculate the amount of overcommitted space for a NAS volume, use: (Total volume space) – (NAS pool capacity) With thin provisioning, storage space is consumed only when data is physically written to the NAS volume, not when the NAS volume is initially allocated. More storage space can be allocated to the NAS volumes than has been allocated in the NAS pool itself.
Snapshot space	Storage space occupied by snapshots of a NAS volume
Data reduction saving	Storage space reclaimed as a result of data reduction processing