Solstice AutoClient 2.1 Administration Guide

Chapter 1 About the AutoClient Technology

The Solstice AutoClient product allows you to set up AutoClient systems and provide centralized administration for these systems. An AutoClient system is a system type that caches (locally stores copies of data as it is referenced) all of its needed system software from a server. AutoClient systems use Solaris^TM diskless and cache file system (CacheFS^TM) technologies.

CacheFS is a general purpose file system caching mechanism that improves NFS^TM server performance and scalability by reducing server and network load. (You can also use CacheFS with HSFS file systems.) The AutoClient technology improves ease of administration, enabling system administrators to maintain many AutoClient systems from a server. Changes do not have to be made on each individual system. Users may notice improved performance as well, on both AutoClient systems and servers.

For more information about CacheFS, see System Administration Guide, Volume I.

This is a list of the overview information in this chapter.

Note -

Throughout this guide, "AutoClient systems" refer to any system that uses the AutoClient technology.

Overview of System Types

System types are basically defined by how they access the root (/) and /usr file systems, including the swap area. For example, standalone and server systems mount these file systems from a local disk, while diskless and dataless clients mount the file systems remotely, relying on servers to provide these services. Table 1-1 lists these and other differences for each system type.

Table 1-1 System Type Overview


System Type	Local File Systems	Local Swap?	Remote File Systems
Server	root (`/`) `/usr` `/home` `/opt` /export `/export/home` `/export/root`	Yes	optional
Standalone System	root (`/`) `/usr` `/export/home`	Yes	optional
Dataless Client	root (`/`)	Yes	`/usr` `/home`
Diskless Client	- none -	No	root (`/`) swap `/usr` `/home`
AutoClient System	cached root (`/`) cached `/usr`	Yes	root (`/`) `/usr` `/home`

Table 1-2 describes how the other clients compare to a standalone system.

Table 1-2 Comparison of Clients Relative to a Standalone System


System Type	Centralized Administration	Performance	System Disk Usage	Network Use
AutoClient System	better	similar	better	similar
Diskless Client	better	worse	better	worse
Dataless Client	similar	worse	better	worse

Server Characteristics

A server system has the following file systems:

The root (/) and /usr file systems, plus swap space
The /export, /export/swap, and /export/home file systems, which support client systems and provide home directories for users
The /opt directory or file system for storing application software

Servers can also contain the following software to support other systems:

OS services for diskless clients and AutoClient systems
Solaris CD image and boot software for networked systems to perform remote installations
JumpStart^TM directory for networked systems to perform custom JumpStart installations

Standalone System Characteristics

A networked standalone system can share information with other systems in the network, but it can function autonomously because it has its own hard disk with enough space to contain the root (/), /usr, and /export/home file systems and swap space. The standalone system thus has local access to operating system software, executables, virtual memory space, and user-created files.

A non-networked standalone system is a standalone system with all the characteristics listed above except that is not connected to a network.

Dataless Clients

A dataless client has local storage for its root (/) file system and swap space. The dataless client cannot function if detached from the network, because its executables (/usr) and user files (/home) are located across the network on the disk of a server.

Note -

SunSoft plans to remove support for dataless clients after Solaris 2.5. You can add this system type now using Host Manager, but in future releases of the Solaris operating environment you will need to choose a different type. It is recommended that you use AutoClient systems instead of dataless clients.

A dataless client places far less demand on the server and the network than a diskless client does. Because dataless clients require less network access, a server can accommodate many more dataless clients than it can diskless clients. Also, since all the user files of all the dataless clients are stored centrally (on a server), they can be backed up and administered centrally.

Diskless Client Characteristics

A diskless client has no disk and depends on a server for all its software and storage area. A diskless client remotely mounts its root (/), /usr, and /home file systems from a server.

A diskless client generates significant network traffic due to its continual need to procure operating system software and virtual memory space from across the network. A diskless client cannot operate if it is detached from the network or if its server malfunctions.

AutoClient System Characteristics

An AutoClient system is nearly identical to a diskless client in terms of installation and administration. It has the following characteristics:

Requires a 100-Mbyte or larger local disk for swapping and for caching its individual root (/) file system and the /usr file system from a server
Can be set up so that it can continue to access its cache when the server is unavailable
Relies on servers to provide other file systems and software applications
Contains no permanent data, making it a field replaceable unit (FRU)

The following figure shows how a server and an AutoClient system work together.

Note -

You must obtain a license for each AutoClient system you want to add to your network. See the Solstice AutoClient 2.1 Installation and Product Notes for licensing information.

Figure 1-1 AutoClient System Characteristics

Why Use an AutoClient System?

AutoClient technology provides many system administration advantages over existing system types.

Advantages Over Diskless Systems

AutoClient systems:

Provide better overall scalability in a network environment, which could result in less network load

Use less disk space on a server than a diskless system (an AutoClient system does not require any swap space on a server)
Use significantly less network and server bandwidth than a diskless system

Advantages Over Dataless and Standalone Systems

AutoClient systems:

Require less system administration overhead. The AutoClient system's data is on a server, which enables centralized administration. For example, with AutoClient systems you only need to back up the server(s) that supports the AutoClient systems. To back up dataless systems, you have to perform a backup on each system. Also, you can manipulate AutoClient root file systems from the server, without accessing each system individually.
Are FRUs, which makes them easy to replace if they fail.
Are installed by setting up an AutoClient system with the Host Manager. You do not have to use the Solaris installation program to install the Solaris environment on an AutoClient system.

How an AutoClient System Works

The CacheFS technology is the important component of AutoClient systems. A cache is a local storage area for data. A cached file system is a local file system that stores files in the cache as they are referenced, and subsequent references to the same files are satisfied from the cache rather than again retrieving them from the server. This functionality reduces the load on the network and the server, and generally results in faster access for the AutoClient system. Note that when the cache becomes full, space is reclaimed on a least recently used (LRU) basis. Files that have been unreferenced for the longest time are discarded from the cache to free space for the files that are currently being referenced.

An AutoClient system uses its local disk for swap space and to cache its individual root (/) file system and the /usr file system from a server's back file systems. Figure 1-2 shows how an AutoClient system works.

Figure 1-2 How an AutoClient System Works

How an AutoClient System's Cache Is Updated

An AutoClient system uses consistency checking to keep a cached file system synchronized with its back file system. The following descriptions show how consistency checking is done for an AutoClient system:

By default, files that are updated in the server's back file systems are updated on the AutoClient system's cached file systems within 24 hours. However, if the update needs to occur sooner, you can use the autosync command. The autosync(1M) command initiates consistency checking that updates (synchronizes) an AutoClient system's cached file systems with its server's back file systems.

For more information about the autosync command, see Chapter 8, AutoClient Environment Maintenance. You can also refer to the autosync(1M) man page.
Each time an AutoClient system is booted, the AutoClient system's cached file systems are checked for consistency and updated with its server's back file systems.

Note -

Consistency checking for an AutoClient system is different from a system running CacheFS. AutoClient files (/ and /usr) are not likely to change very often, so consistency checking does not need to occur as frequently on an AutoClient system as it does on a system running CacheFS. This reduces traffic on your AutoClient network. See System Administration Guide for detailed information about CacheFS consistency checking.

Also, if you add new files to an AutoClient system, its server's back file systems are updated immediately, because an AutoClient system uses a write-through cache. A write-through cache is one that immediately updates its back file system as data is changed or added to the cache.