This chapter concerns the structure of Novell's Network File System (NFS). (Chapter 5 concerns rights in it.) The objectives important to this chapter are:
Key Concepts:It is very important to understand the concepts about file storage. Files that are saved on a local drive are on the workstation itself, and should always be available to the user. Files that are stored on a network drive are stored on a file server, and the user must not only be logged in to the net, but have been assigned necessary privileges to the file and the storage area the file is in. Identify the Basic Components of the Network File SystemMost of the network file system is identical to the Windows file system, however, there is a structure called the volume that is used in the network file system. It represents an area of storage. A volume may be an entire hard disk, a portion of a hard disk, or an area that spans two or more hard disks. This is like a DOS partition, but not the same, since we also use DOS partitions when creating a server. The hierarchy of structures in the network file system places
the volume at the top. However the list on page 4-3 reminds us that a
volume must exist on a server:
In the real world, we should install more than one volume, even if we have only one hard drive, in order to make the file system more robust, more reliable. Identify Guidelines for Planning and Creating Custom Volumes in the Network File SystemManaging the file system is broken into three goals on page 4-4:
The only volume that is created by default on each NetWare server is called SYS. This volume is critical to the functioning of the server.
List the System-Created Directories and Identify Their Contents and FunctionsSo, the SYS: volume is created automatically. In it, several directories are created automatically, and files are placed in many of them. The diagram on page 4-7 shows an illustration of directory names you will need to know. From page 4-8:
Novell warns repeatedly that you should never move, rename or delete any directory created by the system. List Suggested Directories for Organizing the File SystemOn pages 4-9 and 4-10, Novell suggests four additional types of directories
you may want to create:
Identify the Strengths and Weaknesses of Sample Directory StructuresSuggestions follow about creating directory structures. Novell suggests that such structures should
Although the book indicates there are many right answers for the exercises, it is also true that there are many answers that would not meet these guidelines. When considering possibilities, keep in mind the principles above and the fact that the server will stop running if you run out of space in the SYS volume. Identify Utilities to Perform File System Management TasksPage 4-18 lists several utilities for File System management. You have seen ConsoleOne and NetWare Administrator. FILER is an older utility that is text based, not GUI. The other command line utilities listed on page 4-18 are similar to DOS commands. Novell warns us that we should use Novell supplied utilities to manage the file system. Using other utilities may not preserve attributes of the Novell File System. Configure Utilities to View File System InformationThe preferred method of obtaining information about the file system is to use either ConsoleOne or NetWare Administrator. They provide the network administrator with views of objects and information, as well as the means to change them. Some of the things you can do in ConsoleOne are listed on pages 4-24 through 4-27. Things you can do with NetWare Administrator are listed on pages 4-28 and 4-29. Notice that you can view some NetWare file information in Windows Network Neighborhood or Windows Explorer. Novell cautions that attempting to change files through Windows utilities may result in the loss or corruption of this information. In all of these views, notice that a distinction is made between Server objects and Volume objects. The icon for a server looks like a tower PC, while the icon for a volume looks like a filing cabinet. This is one of the few places the NFS and NDS systems come together. Consider them to be different systems. You should be familiar with the information available to you about volumes in NetWare Administrator and in ConsoleOne. Practice viewing this information in the lab. Configure Drive Mappings to Access the File SystemIn order for a user to access portions of the file system, the administrator must create drive pointers that are interpreted by the Novell Client software. You have probably used drive pointers many times, but not thought of them by that name. The standard C: reference for a hard drive is a drive pointer. When the pointer is created on a computer, information is stored that tells the operating system where that drive is located and how to get at it. The act of creating a drive pointer and telling it what to point to is called drive mapping. Drive pointers may be set on individual machines by varied means: using Network Neighborhood or Windows Explorer on a Windows 95 (or later) system, NetWare User Tools on a Windows 3.1x system, or MAP commands on any system with a NetWare client. A user will need to get to various files on a network, and an administrator will have needs to keep users out of various files on the network, so we use various security tools to balance those needs. A common method to set up drive pointers for a number of users is to place mapping commands in a batch or script file that will run when the user logs in to the net. This is usually done automatically for the user, leaving the user unaware that it needs to be done, or that it even can be done. (It was news to most of you, right?) The book gives a good explanation of the methods you might use to create drive mappings in Network Neighborhood. An older method, the MAP command, is discussed elsewhere. The MAP command is used in batch files (and login scripts) to tell Novell Client where files are. A workstation may have access to various kinds of drives:
To map drives using the Windows interface, make sure to read the screen for the options available to you. Remember as well, that a drive mapping is only in effect until it is removed, remapped or the machine is turned off. Mappings that you intend to be "permanent" should be set in the GUI to "reconnect at logon". Identify Which Utilities Manage the Directory StructureRegarding the various utilities to use with file and directory management, study the chart on page 4-34. Notice that anything in this chart can be done with ConsoleOne, NetWare Administrator, or FILER. For certain tasks, you can also use a command line based utility, such as NDIR or NCOPY. Identify Which Utilities Manage FilesThe next important concept is salvaging files. To understand this concept, you must know that when you delete a file, you don't really delete it. When you tell the operating system to delete a file, what it really does is to hide that file from the directory system. If the file does not show in a directory, applications are not aware of it, and the operating system will assume it is not there. The deleted file may as well not be there at all. However, sometimes you want to get a deleted file back, so the salvage process was created. (This is like the "undelete" process in DOS and Windows.) This is related to the objective of identifying which utility to use to manage files (not file structure). The main thing to note is that ConsoleOne cannot be used for file purging or salvaging, nor can it be used to set a file attribute that will cause a file to be purged immediately on deletion. Page 4-36 illustrates the process used to salvage or purge a deleted file. The same interface is used to do either action, so you have to be a bit careful. To salvage a file is to make it visible to the directory system again. To purge a file is to remove it from the hard drive permanently. Since the buttons are next to each other on the screen, you will want to be careful. When a file is deleted, now that you know it does not really get erased, it remains in the directory from which it was deleted. This makes sense: why move it? When you salvage or purge a file, you do it in the directory where the file is. There is one special case, however. If a file has been deleted, and the directory that it is in is also deleted, there would be nowhere to look for that deleted file if you wanted to salvage it. So, when a directory is deleted, any salvageable files in it (deleted, but not purged) are moved to a special directory called DELETED.SAV. They can be salvaged or purged there. In general, deleted files will be available for purging or salvaging unless the volume runs out of empty blocks. A block is a storage unit on a volume, and any file stored on a volume must begin in an empty block. If there are no really empty blocks on a volume, and someone is trying to save a file, the only thing for the system to do is to use a block that holds deleted files. This means that block will lose the part of the deleted file that was stored in it, and you probably will not be able to salvage that file. Such blocks are avoided as long as truly empty blocks are available, then the oldest one is used first. Sometimes you will want to purge some files as soon as they are deleted for security or efficiency. You can set an attribute to do this. Turning on the Purge Immediate attribute for a directory will cause all files in it that are deleted to be purged immediately without further action from you or the user. Configure Volume SpaceNext, we consider managing volume space, starting on page 4-43. As shown earlier in the chapter, you can see statistics on volume space with ConsoleOne, NetWare Administrator, FILER, and the NDIR command. You should be familiar with the use of the NDIR command, especially the chart of variations in syntax shown on page 4-45. The NDIR command is similar to the DOS DIR command. NDIR returns
more information than DIR, and has several soft switches (modifiers) available.
To see information about files in the current directory, type NDIR /FO To see information about directories only, type NDIR /DO To get more information about the syntax of this command, type NDIR /? SYN The idea of limiting space will not seem odd to you if you realize that all disks can fill up, and the system will suffer if they do. Note the two methods of restricting space on page 4-45:
There are other methods of conserving space. File Compression is meant to save space at the expense of time. Files may be stored in a compressed format, saving space, but they must be decompressed before use, costing time. Files and directories may be flagged for "immediate compression" after use (Ic) or they may be flagged as "don't compress" (Dc), if they are always needed at a moment's notice. When a volume is created, file compression may be enabled. If it is enabled, typically, files that are not tagged as "immediate" or "never" are compressed by the system after they have not been used for a specified time. Should the system administrator wish to disable file compression in a volume that is using it, the volume will have to be destroyed and recreated. Block Suballocation allows the hard drive blocks to be used more efficiently. Let's say that on a given hard drive, files are saved in blocks 4 Kilobytes in size. A new file must start in an empty block. If the file is 6 K, then it would actually take up one and a half blocks. Block suballocation allows the system to use the empty 2 K in the second block, which would normally go to waste. This is a good thing. The larger a hard drive is, the larger its blocks are, causing more and more wasted space. Data Migration is the transfer of data not recently used to secondary storage, like an optical disk drive. This is not the same as a backup. It is an automatic process the system carries out, but it requires the installation of HCSS, High Capacity Storage System, as well as the existence of a medium to support it. |