Administrator Guide

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 le is deleted from a thin-provisioned NAS volume, the free space as seen in 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.
Managing NAS Volume Space
FluidFS maintains le metadata in i-node objects. FluidFS i-nodes are 4 KB in size (before metadata replication) and can contain up to 3.5
KB of le data.
When a new virtual volume is created, a portion of it is allocated as i-node area. When a new le is created and there are no free i-nodes
left, an additional portion of the volume is allocated to the i-node area. When a le is deleted, however, the i-node is marked as free (to
make the allocation of new le i-nodes ecient) rather than returned to the free-space pool.
Free i-nodes are returned to the free-space of a volume only when the ratio between the free-space and the number of free i-nodes
becomes very low. When this situation occurs, a special background process is invoked which runs only until the ratio crosses an internal
threshold. The process does not run until all free i-nodes are returned to the free-space.
In deployment environments characterized by large amounts of small les, a massive deletion of small les does not fully reect in the
amount of free-space in the volume. For example, if you lled a 100 TB volume with 70 TB of small les (leaving 30 TB free-space) and
then deleted 50 TB of them, the amount of free-space would likely not increase much. However, as long as the workload remains small-le
oriented, the system reuses the free i-nodes and does not consume from the free-space. Creating some large les requires more space and
eventually return a good portion of the free i-nodes to the free space.
Choosing a Strategy for NAS Volume Creation
When you dene multiple NAS volumes, you can apply dierent management policies — such as data reduction, data protection, le
security style, and quotas — based on your needs.
Consider the following factors to help choose the right strategy based on your environment’s requirements:
• General requirements
– NAS volumes can be created, resized (increased or decreased), or deleted.
– A single NAS volume can contain NFS exports, SMB shares, or a combination of NFS exports and SMB shares.
– The minimum size of a NAS volume is 20 MB. (If the volume has already been used, the minimum size should be more than the
used space or reserved space, whichever is highest.)
• Business requirements – A company or application requirement for separation or for using a single NAS volume must be considered.
NAS volumes can be used to allocate storage for departments on demand, using the threshold mechanism to notify administrators
when they approach the end of their allocated free space.
• Data reduction – Each NAS volume can have a dedicated data reduction policy to best suit the type of data it stores.
• Snapshots – Each NAS volume can have a dedicated snapshot scheduling policy to best protect the type of data it stores.
• Security style – In multiple-protocol environments, it might be benecial to separate the data and dene NAS volumes with UNIX
security style for UNIX/Linux-based clients and NTFS security style for Windows-based clients. This separation enables the
administrator to match the security style with business requirements and various data access patterns. The security style can also be
set to Mixed, which supports both POSIX security and Windows ACLs on the same NAS volume. When a NAS volume is created, the
default le permissions is set to Windows. The settings should be edited immediately after the NAS volume has been created.
• Quotas – Dierent quota policies can be applied to dierent NAS volumes, allowing the administrator to focus on managing quotas
when it is appropriate.
• Replication schedules – Dierent volumes can have dierent replication schedules and policies.
• Auditing SACL SMB Access – Dierent volumes can have dierent policies for handling the auditing of SACL SMB accesses.
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FluidFS Administration