Data Recovery for NSS (Novell Storage Services) : File System for Novell

The Novell Storage Services (NSS) File System is the default file system for NetWare 6 and later. Its many features and capabilities include visibility, a trustee access control model, multiple simultaneous namespace support, native Unicode, user and directory quotas; rich file attributes, multiple data stream support, event file lists, and a file salvage sub-system.

NSS is a 64-bit file system that can manage an unlimited number of file objects. On each physical storage device, NSS abstracts up to four physical NetWare partitions to make them appear as contiguous free space. NSS recognizes physical and logical devices up to 2 TB in size from which you can create any number of virtual storage resources, called pools. You can choose space from at least four devices of up to 2 TB each to create a pool with a maximum pool size of 8 TB. A pool can contain an unlimited number of volumes. If the pool spans devices, the volumes automatically span the devices. A single volume can contain up to 8 trillion files and grow to 8 TB in size, depending on the size of the pool and space consumed by other volumes in the pool.

NSS locates available space on storage devices and logically stores it in a pool. The hard drive partitions that hold the space must be NSS partitions. You can have several partitions, and several pools, but each partition can belong to only one pool. NSS volumes are created from the storage space in the pool. Up to 255 logical volumes can be created in a pool.

The NSS service first scans hard drives for unused space. Whatever space is found is marked off, labeled as available to NSS, and recorded in a pool called the NSS object bank. This action is registering the space. Each of several hard drives may have free space available. NSS can register space in NetWare partitions and in IBM-formatted (DOS) partitions.

However, this action is essentially creating an NSS partition on the hard drive, and that there is a limit of four partitions within any IBM-formatted partition. If an IBM/DOS partition already has four partitions in it, you cannot make an NSS partition in it. This is why you do not want to create partitions within your DOS partition on the server.When NSS takes free space from a NetWare partition, NFS sees the new NSS partition as a file.

NSS is designed to make use of storage space regardless of its location. To accomplish this, an additional abstraction layers is added to file system management. NSS provides the support to add storage devices to your system without having to create new volumes. NSS architecture consists of five interface layers that work together to present multiple storage devices as a single, cohesive file system to users. These interfaces are as under:

Storage devices

NSS storage devices are simply hardware components that store NetWare data as electronic bits. These Storage devices include hard drives, CD-ROM drives, and offline storage media (such as tape devices). In NSS the storage devices are organized independently from volumes, and can therefore be added and removed from your network without adversely affecting volume architecture.

Storage deposits

Storage deposits are effectively free space. NSS gathers free space from unpartitioned areas of storage devices or available free space inside existing NetWare volumes. When NSS removes free space from a NetWare volume, the traditional file system acknowledges the reduction in free space and identifies the storage deposit as a file. Storage deposits are further organized into partitions.

Partitions

Partitions are pieces of storage deposits that are configured for a specific operating system. In NSS, partitions are typically configured for NetWare. These partitions are organized into storage pools.

Storage pools

Storage pools are created after partitions but before NSS logical volumes. A storage pool is a specific amount of file system space which can be obtained from storage devices. After the creation of a pool, storage devices can be added to your server without affecting the volume hierarchy. The basic logical abstraction layer between NetWare volumes and multiple storage devices are the storage pools.

Volumes

Logical volumes, traditional volumes, and read-only volumes are supported by NSS. Logical volumes are subsets of NSS storage pools that can be set to a specific size or allowed to grow dynamically according to the amount of physical space in the pool. Traditional volumes are also supported in NetWare 6, but do not reference storage pools. Instead, traditional volumes must be created directly as subsets of partitions. Read-only volumes are physical file system objects that reference CD-ROM storage devices. The most significant point about NSS is that it supports multiple volume types concurrently.

Configure NSS Volume Attributes

NSS volumes have a large set of attributes which can be set as options. The attributes which are not needed should not be turned on because they can reduce performance of the volume.

Backup - Turn this on to enable backups. This does not perform a backup, it just allows it.
Compression - Turn this on to make this a compressed volume. Once enabled, you cannot turn this feature off.
Migration - Turn this on to enable migration of old files to specified locations.
Modified file list - This provides a list of files modified since last backup. Your backup software must recognize this feature for it to be of use.
Salvage files - This feature preserves deleted files for data recovery.
Snapshot - This feature allows a backup utility to make a copy of the last saved version of files that are open when the backup is made. Without this feature, any opened files are ignored by the backup.
User space restrictions - This allows you to set space limits for individual users.
Data shredding – Data shredding feature causes random characters to be written over deleted files. We can set the process to take place from one to seven times, to reduce the chance of recovering a deleted file.
Directory quotas - Turn this on to be able do set space limits for directories.
Flush files immediately - Turning on this feature means that when you finish working on a file from this volume, changes to the file are written to the volume immediately.
User-level transaction model - This feature protects database files from damage in case of network failures. It serves as the rollback service that NDS.DB provides to eDirectory.

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