Administrator Guide

Managing NAS Volume Space
FluidFS maintains file 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 file data.
When a new virtual volume is created, a portion of it is allocated as i-node area. When a new file 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 file is deleted, however, the i-node is marked as free (to
make the allocation of new file i-nodes efficient) 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 files, a massive deletion of small files does not fully reflect in the
amount of free-space in the volume. For example, if you filled a 100 TB volume with 70 TB of small files (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-file
oriented, the system reuses the free i-nodes and does not consume from the free-space. Creating some large files 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 define multiple NAS volumes, you can apply different management policies — such as data reduction, data protection, file
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 beneficial to separate the data and define 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 file permissions is set to Windows. The settings should be edited immediately after the NAS volume has been created.
• Quotas – Different quota policies can be applied to different NAS volumes, allowing the administrator to focus on managing quotas
when it is appropriate.
• Replication schedules – Different volumes can have different replication schedules and policies.
• Auditing SACL SMB Access – Different volumes can have different policies for handling the auditing of SACL SMB accesses.
Examples of NAS Volume Creation
This section includes examples that show how NAS volumes can be created to meet the needs of an organization with the departments
and NAS volume requirements described in the following table.
Department
Security
Style
Snapshots Replication NDMP
Backup
Number of
SMB/NFS
Clients
Read/Write
Mix
Hourly
Change % of
Existing Data
Post Production UNIX Hourly No Weekly 20 20/80 1%
Administration
and Finance
NTFS No No Weekly 10 50/50 None
Broadcast Mixed No No Weekly 10 90/10 None
Press NTFS Daily No No 5 10/90 5%
Marketing NTFS Daily Yes No 5 50/50 None
An average read/write mix is 20/80. An average hourly change rate for existing data is less than 1 percent.
FluidFS Administration
379