NSS helps improve the scalability, flexibility, and availability of your storage devices. This section identifies specific NSS features that help you do the following:
NSS requires only about 1 MB of server memory to activate a volume, independent of the number of files it contains. With NSS, you can activate up to 256 NSS volumes concurrently per server, up to the available server memory.
Whenever you activate an NSS volume, it takes only seconds to mount a volume instead of minutes. NSS uses a journaling file system and does not need to scan the entire file system to create a directory entry table (DET) to load the volume. NSS loads a file’s metadata into the memory only when you access the file.
NSS reads the file system journal only if a server goes down abnormally. Instead of slowly searching the volume for errors, NSS reads the journal to identify any incomplete transactions. It either completes the transaction or backs it out. This results in less server down time and is beneficial for applications such as mail services.
NSS provides the following features to improve I/O performance and provide fault-tolerant access to your data:
Software RAID support for RAIDs 0, 1, 5, 0+1, and 5+1
Uses software RAID devices to improve performance and availability. For information, see Section 14.0, Managing NSS Software RAID Devices.
Makes devices shareable for use in a cluster. For information, see Section 11.6, Sharing Devices.
Multiple name space support
NSS provides full support for filenames in the Long, UNIX, DOS, and Macintosh name spaces. Long name space is the default. For information, see Lookup Namespace.
Rich file metadata support
NSS provides full support for all file attributes and multiple simultaneous data streams for DOS, Windows, UNIX, and Macintosh. For information, see Section 21.1, Configuring File System Trustees, Trustee Rights, Inherited Rights Filters, and Attributes.
NSS includes the following features to help prevent access to data that circumvents normal access control:
Encrypted Volume Support
Encrypts data volumes, meeting U.S. Government security standards. For information, see Managing Encrypted NSS Volumes.
Data shredding (up to 7 times) for deleted files
Erases files completely, meeting U.S. Government security standards. For information, see Section 21.3, Using Data Shredding to Prevent Access to Purged Files.
Multiple Server Access Prevention for pools
Ensures data integrity by preventing unauthorized access to shared media in a storage area network. For information, see Section 16.13, Preventing Pools from Activating on Multiple Servers.
Trustee model for access control on NSS volumes
NSS uses the OES Trustee model to greatly simplify access control management in the file system. It restricts visibility of data structures so that users only see subdirectories they have rights to see, not the whole tree like all other file systems.
For information about the OES Trustee model and NSS file system rights, see the OES 2015 SP1: File Systems Management Guide.
Some additional steps are necessary to configure access control for NSS. For information, see Section 6.5, Access Control for NSS.
NSS includes the following features to ensure that the most current copy of your data is recoverable:
Pool snapshots to provide point-in-time views of data
Backs up files from snapshots of data so that all files, including open ones, are backed up. For information, see Managing NSS Pool Snapshots.
Immediate data saves
Writes data to the volume at regular intervals in order to reduce the seek time on the drive. For information, see Section 28.3, Configuring or Tuning Group I/O.
Salvage file subsystem
Recovers files, directories, and volumes that were deleted by applications or from the terminal/console commands. For information, see Salvaging and Purging Deleted Volumes, Directories, and Files.
NSS includes the following features to help you maximize your available space:
Compresses inactive files, according to preset parameters, to conserve space in a volume. For information, see Managing Compression on NSS Volumes.
Volume space restrictions
Limits the amount of space a volume can consume in its pool. For information, see Section 23.2, Managing NSS Volume Quotas.
Directory space restrictions
Limits the amount of space a subdirectory can consume, regardless of broader volume and user constraints. For information, see Section 23.3, Managing Directory Quotas.
User space restrictions
Limits the amount of space a user’s data can consume, regardless of broader directory or volume constraints. For information, see Section 23.4, Managing User Space Quotas.
Delayed block allocation in NSS improves the locality of sequential file content on a disk and thereby reduces the disk fragmentation.
Buffered writes is the only supported write mechanism in NSS. During buffered writes, delayed block allocation allows aggregation of sequential file blocks before writing them to the disk. The aggregation of sequential file blocks allows all the blocks to be allocated as a single extent (set of contiguous disk blocks) instead of separate disk blocks, if they were allocated at user write time. This locality of sequential file blocks on disk helps to improve the access time during the sequential read work loads such as filesystem reads or backup.
Even writes of such blocks into disks perform better as it minimizes the rotational and seek latencies involved in the movement of disk head in a rotational disk, compared to the traditional block allocation.
Delayed block allocation also reduces the writes of NSS metadata such as journal, fileMap, freeTree and logged pool or volume as it now updates each of these metadata for all aggregated sequential file blocks instead of individual user file block writes.
This feature is not applicable for the volumes that enabled with Compression, User quota, and Directory quota features.