Dell Storage Manager 2020 R1 Administrator's Guide

Thin and Thick Provisioning for NAS Volumes

In addition to the thin provisioning applied to the NAS pool, NAS volumes can be thin‑provisioned. With thin provisioning (the default), storage space is consumed on the Storage Centers only when data is physically written to the NAS volume, not when the NAS volume is initially allocated. Thin provisioning offers the flexibility to modify NAS volumes to account for future increases in usage. However, because it is possible for the storage space used by the NAS volumes to exceed the Storage Center space allocated to the NAS pool, you must monitor available capacity on the Storage Centers to ensure that the FluidFS cluster always has sufficient free space available. You can also specify a portion of the NAS volume (reserved space) that is dedicated to the NAS volume (no other volumes can take the space). The total reserved space of all NAS volumes cannot exceed the available capacity of the NAS pool.

If a file is deleted from a thin-provisioned NAS volume, the free space as seen in Dell Storage Manager increases. The freed-up capacity is also visible and available to clients in the SMB shares or NFS exports. However, the Storage Center does not report any capacity freed up in the NAS pool unless you enable the SCSI Unmap feature.

Thick provisioning allows you to allocate storage space on the Storage Centers statically to a NAS volume (no other volumes can take the space). Thick provisioning is appropriate if your environment requires guaranteed space for a NAS volume.