Understanding NSS

Test Objective Covered:

1. Identify how NSS works.

As network users and applications have become more sophisticated in the twenty-first century, so has their insatiable appetite for storage. One of the greatest demands you will face is the need for more storage, larger files, more efficient file management, and faster volume mounting speeds. NSS is the answer.

NSS is a 64-bit file storage system that enables you to configure, mount, and maintain large volumes. NSS is best suited for networks that need to store and maintain large volumes, numerous files, or large databases. Does that sound like your network?

In this first lesson, we will explore the sophisticated NSS architecture and examine its plethora of features in five different categories: performance, reliability, security, storage, and management. But before we dive into the NSS architecture, let's summarize the differences between NetWare 6 NSS and the traditional file system.

NSS is an extension of the traditional NetWare file system. In NSS, storage devices are organized into storage deposits and partitions are organized into storage pools. Table 5.1 compares key NSS improvements to NetWare's traditional file system.

Table 5.1. Comparing NetWare 6's Two File Systems: NSS Versus Traditional

FEATURE	NSS FILE SYSTEM	TRADITIONAL FILE SYSTEM
Architecture Components	Storage device, storage deposit, partition, storage pool, volume	Storage device, partition,volume
Maximum File Size	8TB (terabytes)	2GB
Files per Volume	8 trillion	16 million
Volume Mounting Performance	Seconds	Minutes
Simultaneously Mounted Volumes	255	8
Management Tools	ConsoleOne, Remote Manager	ConsoleOne, Remote Manager

Unfortunately, there's a downside to this wonderful NSS story. With all of its power, NSS does not support the following two features:

• Block suballocation

• Auditing

Despite these current limitations, you will want to use NSS as your primary (and maybe exclusive) file system in NetWare 6. NSS provides you with the advances of high storage capacity and increased data access performance. Now let's take a closer look at how NSS accomplishes all these miracles by exploring its sophisticated architecture.

NSS Architecture

NSS is designed to make use of storage space regardless of its location. To accomplish this, Novell has added additional abstraction layers to file system management. As shown in Figure 5.2, the primary architecture differences between NSS and the traditional file system focus on two abstraction layers: storage deposits and storage pools. NSS also supports logical volumes that enable you to add storage devices to your system without having to create new volumes.

Figure 5.2. NSS and traditional file system architectures.

NSS architecture consists of five interface layers that work together to present multiple storage devices as a single, cohesive file system to users. The five layers are illustrated in Figure 5.2 and described in the following text:

• Storage Devices NSS storage devices are simply hardware components that store NetWare data as electronic bits. Storage devices include hard drives, CD-ROM drives, and offline storage media (such as tape devices). The beauty of NSS is that storage devices are organized independently from volumes, and therefore, can be added and removed from your network without adversely affecting volume architecture. Of course, data files that reside on storage devices that have been removed are no longer available to users.

• 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 have been configured for a specific operating system. In the case of NSS, partitions are typically configured for NetWare. Partitions are further organized into NSS storage pools.

• Storage Pools A storage pool is a specific amount of file system space that is obtained from one or more storage devices. Storage pools are created after partitions but before NSS logical volumes. After a pool is created, you can add storage devices to your server without affecting the volume hierarchy. Storage pools are the primary logical abstraction layer between NetWare volumes and multiple storage devices. Storage pools are further organized into volumes.

• Volumes NSS supports three types of volumes: logical volumes, traditional volumes, and read-only volumes. Logical volumes are new to NetWare 6. They 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 you have in your pool. A single volume cannot be larger than its host storage pool because all NSS logical volumes must reside in a single pool. By default, NetWare 6 creates a storage pool named SYS and an equally sized logical volume named SYS:. 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, as shown in Figure 5.2. Read-only volumes are physical file system objects that reference CD-ROM storage devices. The cool thing about NSS is that it supports multiple volume types simultaneously.

Clearly, NSS is much more complex than the traditional file system. The good news is that most of its architecture is transparent to users. The storage pool layer allows you to add and subtract storage devices without affecting the file system hierarchy. This is a critical improvement over the fixed architecture found in earlier versions of NetWare.

NSS Features

NSS embraces state-of-the-art file system technology. In this section, we will explore some of its most exciting features including multiple logical volumes, overbooking, data recovery, clustering, data shredding, hot fix, and software RAID support. These features are organized into the following five categories:

• NSS Performance Features

• NSS Reliability Features

• NSS Security Features

• NSS Storage Features

• NSS Management Features

NSS Performance Features

NSS includes these three performance features:

• Volume Mounting Speed When you mount volumes using the traditional file system, NetWare scans every file and directory while mounting, then loads the File Access Table (FAT) into memory for quick access. If you increase the number or size of files, the traditional file system allocates memory from your available server pool. This process takes a long time and places a burden on server RAM. NSS, on the other hand, doesn't require additional memory to mount large volumes because it skips the entire scanning process. In fact, NSS doesn't load the FAT into memory until you access files. Therefore, increasing volume size or the number of files stored does not require additional memory; volume mounting is very fast.

• File Flushing By default, NetWare 6 queues file modifications in memory until processor utilization is low. At that point, NSS writes such changes to disk (that is, flushes them). This feature improves file saving and server performance by delaying queue operations until the processor is available. File flushing does, however, put data at risk if a server crash occurs during the queuing period. Fortunately, NSS includes a Flush Files Immediately parameter that overrides file flushing and increases data reliability (but decreases file saving and server performance).

• Software RAID Redundant Array of Independent Disks (RAID) is an industry-wide standard for storing the same data in different places on multiple hard drives. By reading and writing data across multiple storage devices, disk I/O processes can be balanced, which significantly improves the performance of the file system. NetWare 6 NSS provides a software option that emulates a hardware RAID system. NSS software RAID comes in two flavors: data striping (Level 0) and mirroring (Level 1).

NOTE

Software RAID configuration is discussed in depth in the "Configuring NSS" lesson of this chapter.

NSS Reliability Features

NSS includes these five reliability features:

• Data Recovery NSS can quickly recover data after a file system crash. How does this work? Instead of scanning an entire volume for corruption, NSS reviews the last known set of changes to the file system to ensure they were written correctly. NSS either recovers the changed information or returns the data to its original settings before the transaction began (known as roll-back).

• File Snapshot The File Snapshot feature in NSS automatically stores an original copy of all open files. This feature ensures that if you lose data between backup cycles, you still have a valid copy of the previously saved file. This helps ensure that your backup utility has a consistent copy of all files.

• Modified File List (MFL) The Modified File List (MFL) is a list of files that changed since the previous backup. Your backup utility can access this list instead of searching the entire file system for modified files. Think of MFL as a FAT for modified files.

• Clustering NetWare 6 NSS supports volume clustering via Novell Cluster Services (NCS) version 1.6. Clustering is a high-availability solution for fault tolerance of your critical network resources including data applications, server licenses, and network services. In a nutshell, clustering allows two NetWare 6 servers to share high-speed hard disks. This way, if anything happens to any of the server components, the data is still available.

  For more information about the high-availability solution for fault tolerance with clustering, see Chapter 7.

• Hot Fix Hot Fix is a redirection strategy that NSS uses to ensure that server data isn't written to unreliable areas of a given storage device. With Hot Fix, data is redirected to the Hot Fix redirection area of a hard disk partition when unreliable blocks are encountered on the disk. When redirecting a block of data, the operating system records the address of the defective block so that no future attempts are made to write to that area. You must configure Hot Fix when you create NSS partitions. To add Hot Fix after volumes have been created, you must delete the host volume from the partition list, add Hot Fix, and then restore the volume from backup media. Because Hot Fix is associated with NSS mirroring, both features are enabled when you turn on Hot Fix. By default, two percent of a disk's space is set aside as the Hot Fix redirection area you can increase or decrease this amount.

NSS Security Features

NSS includes these three security features:

• Data Shredding NSS data shredding adds a measure of security to your network by overwriting purged disk blocks with a random pattern of hexidecimal characters. This prevents unauthorized individuals from recovering purged files using a disk editor. You can place up to seven data shred patterns over deleted data think of this as an electronic paper shredder for your server disks.

• User Space Restrictions NSS User Space Restrictions allow you to limit the space users have on specific volumes. When you create a volume, you can select the User Space Restriction option in ConsoleOne and restrict users to their own virtual area of the file system. This security feature prevents users from affecting other parts of the drive by placing unnecessary storage demands on the server.

• Directory Space Restrictions NSS Directory Space Restrictions allow you to limit the space users have in a specific directory or subdirectory. This feature is similar to User Space Restrictions except that the restriction is at the directory level instead of at the user level.

NSS Storage Features

NSS includes these four storage features:

• Multiple Logical Volumes NSS allows you to create multiple logical volumes within a single storage pool. This feature allows you to distribute multiple storage devices through a single storage pool to multiple logical volumes. You can also add storage devices to logical volumes without changing the volume hierarchy or impacting existing data.

• Overbooking Overbooking is NSS synergy: The whole is greater than the sum of the parts. This feature allows you to configure the sum of the sizes of each volume in a storage pool to exceed the pool size. For example, you may have users assigned to volumes with a limited amount of space. You can assign volumes that collectively exceed the pool size if not all users fill up their volumes. NSS can also borrow space from other volumes in a given pool as long as those volumes are not filled to the limit. While overbooking is an efficient NSS storage feature, you should use it cautiously because volumes can prematurely run out of disk space when storage pools are overbooked.

• File Compression When enabled, NSS automatically compresses inactive files to create additional disk space. One word of warning: Once you enable file compression, you cannot turn it off without re-creating the volume! NetWare 6 includes a variety of SET parameters that enable you to manage the performance and efficiency of NSS file compression.

• CD Support NSS has full CD-ROM support for the following two format standards: ISO 9660 and HFS. NSS CD-ROM devices map directly to read-only volumes. NSS integrates and mounts CD-ROM volumes automatically.

NSS Management Features

NSS includes the management feature of Storage Pool Maintenance. With NSS, data storage maintenance is much less disruptive than with the traditional file system. Instead of bringing down the server for routine maintenance, you can deactivate individual storage pools while the server is running. You can use ConsoleOne or Remote Manager to configure and maintain NSS storage pools and volumes. Remember that when you deactivate a storage pool, users cannot access the volumes in that pool until it is reactivated.

TIP

The NWCONFIG and NSS Menu utilities that were used to manage NSS in prior versions of NetWare are not compatible with the current version of NSS. In NetWare 6, you must use ConsoleOne or Remote Manager to configure and maintain both traditional and NSS logical volumes.

This completes our lesson in the basic architecture and features of NSS. As you have learned, this new storage technology is a huge improvement over the traditional NetWare file system. The good news is that most of this sophistication is transparent to users. The bad news is that network administrators must learn much more about how to configure and manage this new architecture. Fortunately, that is the subject of our next lesson, Configuring NSS.