Types of Oracle Solaris File Systems

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The Oracle Solaris OS supports three types of file systems:

Disk-based
Network-based
Virtual

To identify the file system type, see Determining a File System's Type.

Oracle Solaris Disk-Based File Systems

Disk-based file systems are stored on physical media such as hard disks and DVDs. Disk-based file systems can be written in different formats. The available formats are described in the following table.

Disk-Based File System	Format Description
ZFS	ZFS is the default disk-based and root file system.
UFS	Legacy UNIX file system (based on the BSD Fat Fast File system that was provided in the 4.3 Tahoe release).
PxFS	Oracle Solaris Cluster software provides a cluster file system based on the Oracle Solaris Cluster Proxy File System (PxFS).
SAM-QFS	SAM-QFS is an integrated hierarchical storage manager (HSM) and storage area network (SAN) file system. SAM is the HSM storage and archive management component. QFS is the SAN scalable high performance file system component. SAM-QFS also has integrated disk volume management and tape volume management. QFS also has a write once, read many times (WORM) file system capability. QFS can be used independently of SAM when just a file system is needed. SAM requires QFS and cannot be used independently of QFS.
HSFS	High Sierra, Rock Ridge, and ISO 9660 file system. High Sierra is the first CD-ROM file system. ISO 9660 is the official standard version of the High Sierra file system. The HSFS file system is used on CD-ROMs, and is a read-only file system. Oracle Solaris HSFS supports Rock Ridge extensions to ISO 9660. When present on a CD-ROM, these extensions provide all file system features and file types, except for writability and hard links.
PCFS	PC file system, which allows read- and write- access to data and programs on DOS-formatted disks that are written for DOS-based personal computers.
UDFS	The Universal Disk Format (UDFS) file system, the industry-standard format for storing information on the optical media technology called DVD (Digital Versatile Disc or Digital Video Disc).

Each type of disk-based file system is customarily associated with a particular media device, as follows:

ZFS or UFS with hard disk
HSFS with CD-ROM
PCFS with USB diskette
UDF with DVD
SAM-QFS with a hard disk or tape
PxFS with a hard disk - For a cluster file system to be highly available, the underlying disk storage must be connected to more than one Oracle Solaris host. Therefore, a local file system (a file system that is stored on a host's local disk) that is made into a cluster file system is not highly available. For more information, see Cluster File Systems in Oracle Solaris Cluster Concepts Guide .

However, these associations are not restrictive. For example, DVDs can have ZFS or UFS file systems created on them.

The Universal Disk Format (UDFS) File System

For information about creating a UDFS file system on removable media, see How to Create a File System on Removable Media in Managing Devices in Oracle Solaris 11.2 .

The UDF file system is the industry-standard format for storing information on DVD (Digital Versatile Disc or Digital Video Disc) optical media.

The UDF file system is provided as dynamically loadable 32-bit and 64-bit modules, with system administration utilities for creating, mounting, and checking the file system on both SPARC and x86 platforms. The Oracle Solaris UDF file system works with supported ATAPI and SCSI DVD drives, CD-ROM devices, and disk drives. In addition, the Oracle Solaris UDF file system is fully compliant with the UDF 1.50 specification.

The UDF file system provides the following features:

Ability to access the industry-standard CD-ROM and DVD-ROM media when they contain a UDF file system
Flexibility in exchanging information across platforms and operating systems
A mechanism for implementing new applications rich in broadcast-quality video, high-quality sound, and interactivity using the DVD video specification based on UDF format

The following features are not included in the UDF file system:

Support for write-once media, (CD-RW), with either the sequential disk-at-once recording and incremental recording

The UDF file system requires the following:

Supported SPARC or x86 platform
Supported CD-ROM or DVD-ROM device

The Oracle Solaris UDF file system implementation provides the following:

Support for industry-standard read/write UDF version 1.50
Fully internationalized file system utilities

Network-Based File Systems

Network-based file systems can be accessed from the network. Typically, network-based file systems reside on one system, typically a server, and are accessed by other systems across the network.

With the NFS service, you can provide distributed resources (files or directories) by sharing them from a server and mounting them on individual clients. For more information, see The NFS Environment.

With the Oracle SMB service, you can provide distributed resources (files or directories) to Windows and Mac OS systems by sharing them from a server and mounting them on individual clients. For more information, see The Oracle Solaris SMB Service.

Virtual File Systems

Virtual file systems are memory-based file systems that provide access to special kernel information and facilities. Most virtual file systems do not use file system disk space. Also, some virtual file systems, such as the temporary file system (TMPFS), use the swap space on a disk.

Temporary File System

The temporary file system (TMPFS) uses local memory for file system reads and writes. Using TMPFS can improve system performance by saving the cost of reading and writing temporary files to a local disk or across the network. For example, temporary files are created when you compile a program. The OS generates a much disk activity or network activity while manipulating these files. Using TMPFS to hold these temporary files can significantly speed up their creation, manipulation, and deletion.

Files in TMPFS file systems are not permanent. These files are deleted when the file system is unmounted and when the system is shut down or rebooted.

TMPFS is the default file system type for the /tmp directory in the Oracle Solaris OS. You can copy or move files into or out of the /tmp directory, just as you would in a ZFS or UFS file system. The TMPFS file system uses swap space as a temporary backing store.

If a system with a TMPFS file system does not have adequate swap space, two problems can occur:

The TMPFS file system can run out of space, just as regular file systems do.
Because TMPFS allocates swap space to save file data (if necessary), some programs might not execute because of insufficient swap space.

For information about creating TMPFS file systems, see Chapter 2, Creating and Mounting File Systems. For information about increasing swap space, see Chapter 3, Configuring Additional Swap Space.

The Loopback File System

The loopback file system (LOFS) lets you create a new virtual file system so that you can access files by using an alternative path name. For example, you can create a loopback mount of the root (/) directory on /tmp/newroot. This loopback mounts make the entire file system hierarchy appear as if it is duplicated under /tmp/newroot, including any file systems mounted from NFS servers. All files will be accessible either with a path name starting from root (/), or with a path name that starts from /tmp/newroot.

For information on how to create LOFS file systems, see Chapter 2, Creating and Mounting File Systems.

Process File System

The process file system (PROCFS) resides in memory and contains a list of active processes, by process number, in the /proc directory. Information in the /proc directory is used by commands such as ps. Debuggers and other development tools can also access the address space of the processes by using file system calls.

Caution - Do not delete files in the /proc directory. The deletion of processes from the /proc directory does not kill them. /proc files do not use disk space, so there is no reason to delete files from this directory.

The /proc directory does not require administration.

Additional Virtual File Systems

These additional types of virtual file systems are listed for your information. They do not require administration.

Virtual File System	Description
CTFS	CTFS (the contract file system) is the interface for creating, controlling, and observing contracts. A contract enhances the relationship between a process and the system resources it depends on by providing richer error reporting and (optionally) a means of delaying the removal of a resource. The service management facility (SMF) uses process contracts (a type of contract) to track the processes which compose a service, so that a failure in a part of a multi-process service can be identified as a failure of that service.
FIFOFS (first-in first-out)	Named pipe files that give processes common access to data.
FDFS (file descriptors)	Provides explicit names for opening files by using file descriptors.
MNTFS	Provides read-only access to the table of mounted file systems for the local system.
NAMEFS	Used mostly by STREAMS for dynamic mounts of file descriptors on top of files.
OBJFS	The OBJFS (object) file system describes the state of all modules currently loaded by the kernel. This file system is used by debuggers to access information about kernel symbols without having to access the kernel directly.
SHAREFS	Provides read-only access to the table of shared file systems for the local system.
SPECFS (special)	Provides access to character special devices and block devices.
SWAPFS	Used by the kernel for swapping.

Extended File Attributes

The ZFS, UFS, NFS, and TMPFS file systems have been enhanced to include extended file attributes. Extended file attributes enable application developers to associate specific attributes to a file. For example, a developer of an application used to manage a windowing system might choose to associate a display icon with a file. Extended file attributes are logically represented as files within a hidden directory that is associated with the target file.

You can use the runat command to add attributes and execute shell commands in the extended attribute namespace. This namespace is a hidden attribute directory that is associated with the specified file.

To use the runat command to add attributes to a file, you first have to create the attributes file.

$ runat filea cp /tmp/attrdata attr.1

Then, use the runat command to list the attributes of the file.

$ runat filea ls -l

For more information, see runat (1) .

Many Oracle Solaris file system commands have been modified to support file system attributes by providing an attribute-aware option. Use this option to query, copy, or find file attributes. For more information, see the specific man page for each file system command.

Swap Space

The Oracle Solaris OS uses some disk slices for temporary storage rather than for file systems. These slices are called swap slices, or swap space. Swap space is used for virtual memory storage areas when the system does not have enough physical memory to handle current processes.

Since many applications rely on swap space, you should know how to plan for, monitor, and add more swap space, when needed. For an overview about swap space and instructions for adding swap space, see Chapter 3, Configuring Additional Swap Space.