Write Ahead Physical Block Logging (WAPBL) provides meta data journaling for file systems in conjunction with Fast File System (FFS) to accomplish rapid filesystem consistency after an unclean shutdown of the filesystem and better general use performance over regular FFS. [1] [2] [3] [4] With the journal, fsck is no longer required at system boot; instead, the system can replay the journal in order to correct any inconsistencies in the filesystem if the system has been shut down in an unclean fashion. [3]
WAPBL was initially committed into NetBSD in 2008, and first appeared with NetBSD 5.0 (2009). [5] [2] [6]
With NetBSD 6.0 (2012), soft updates (known as soft dependencies in NetBSD) was removed in favour of WAPBL. [7] [8]
XFS is a high-performance 64-bit journaling file system created by Silicon Graphics, Inc (SGI) in 1993. It was the default file system in SGI's IRIX operating system starting with its version 5.3. XFS was ported to the Linux kernel in 2001; as of June 2014, XFS is supported by most Linux distributions; Red Hat Enterprise Linux uses it as default filesystem.
AmigaDOS is the disk operating system of the AmigaOS, which includes file systems, file and directory manipulation, the command-line interface, and file redirection.
The Unix file system (UFS) is a file system supported by many Unix and Unix-like operating systems. It is a distant descendant of the original filesystem used by Version 7 Unix.
The Filesystem Hierarchy Standard (FHS) is a reference describing the conventions used for the layout of a UNIX system. It has been made popular by its use in GNU/Linux distributions, but it is used by other UNIX variants as well. It is maintained by the Linux Foundation. The latest version is 3.0, released on 3 June 2015.
The Amiga Fast File System is a file system used on the Amiga personal computer. The previous Amiga filesystem was never given a specific name and known originally simply as "DOS" or AmigaDOS. Upon the release of FFS, the original filesystem became known as Amiga Old File System (OFS). OFS, which was primarily designed for use with floppy disks, had been proving slow to keep up with hard drives of the era. FFS was designed as a full replacement for the original Amiga filesystem. FFS differs from its predecessor mainly in the removal of redundant information. Data blocks contain nothing but data, allowing the filesystem to manage the transfer of large chunks of data directly from the host adapter to the final destination.
Soft updates is an approach to maintaining file system meta-data integrity in the event of a crash or power outage. Soft updates work by tracking and enforcing dependencies among updates to file system meta-data. Soft updates are an alternative to the more commonly used approach of journaling file systems.
The proc filesystem (procfs) is a special filesystem in Unix-like operating systems that presents information about processes and other system information in a hierarchical file-like structure, providing a more convenient and standardized method for dynamically accessing process data held in the kernel than traditional tracing methods or direct access to kernel memory. Typically, it is mapped to a mount point named /proc at boot time. The proc file system acts as an interface to internal data structures about running processes in the kernel. In Linux, it can also be used to obtain information about the kernel and to change certain kernel parameters at runtime (sysctl).
The Log-Structured File System is an implementation of a log-structured file system, originally developed for BSD. It was removed from FreeBSD and OpenBSD; the NetBSD implementation was nonfunctional until work leading up to the 4.0 release made it viable again as a production file system.
sync is a standard system call in the Unix operating system, which commits all data in the kernel filesystem to non-volatile storage buffers, i.e., data which has been scheduled for writing via low-level I/O system calls. Higher-level I/O layers such as stdio may maintain separate buffers of their own.
The following tables compare general and technical information for a number of file systems.
Btrfs is a computer storage format that combines a file system based on the copy-on-write (COW) principle with a logical volume manager, developed together. It was initially designed at Oracle Corporation in 2007 for use in Linux, and since November 2013, the file system's on-disk format has been declared stable in the Linux kernel. According to Oracle, Btrfs "is not a true acronym".
In Unix-like operating systems, a device file or special file is an interface to a device driver that appears in a file system as if it were an ordinary file. There are also special files in DOS, OS/2, and Windows. These special files allow an application program to interact with a device by using its device driver via standard input/output system calls. Using standard system calls simplifies many programming tasks, and leads to consistent user-space I/O mechanisms regardless of device features and functions.
Toybox is a free and open-source software implementation of over 200 Unix command line utilities such as ls, cp, and mv. The Toybox project was started in 2006, and became a 0BSD licensed BusyBox alternative. Toybox is used for most of Android's command line tools in all currently supported Android versions, and is also used to build Android on Linux and macOS. All of the tools are tested on Linux, and many of them also work on BSD and macOS.
A flash file system is a file system designed for storing files on flash memory–based storage devices. While flash file systems are closely related to file systems in general, they are optimized for the nature and characteristics of flash memory, and for use in particular operating systems.
HAMMER is a high-availability 64-bit file system developed by Matthew Dillon for DragonFly BSD using B+ trees. Its major features include infinite NFS-exportable snapshots, master-multislave operation, configurable history retention, fsckless-mount, and checksums to deal with data corruption. HAMMER also supports data block deduplication, meaning that identical data blocks will be stored only once on a file system. A successor, HAMMER2, was announced in 2011 and became the default in Dragonfly 5.2.
A journaling file system is a file system that keeps track of changes not yet committed to the file system's main part by recording the goal of such changes in a data structure known as a "journal", which is usually a circular log. In the event of a system crash or power failure, such file systems can be brought back online more quickly with a lower likelihood of becoming corrupted.
NetBSD is a free and open-source Unix-like operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is available for many platforms, including servers, desktops, handheld devices, and embedded systems.
The envsys framework is a kernel-level hardware monitoring sensors framework in NetBSD. As of 4 March 2019, the framework is used by close to 85 device drivers to export various environmental monitoring sensors, as evidenced by references of the sysmon_envsys_register symbol within the sys path of NetBSD; with temperature sensors, ENVSYS_STEMP, being the most likely type to be exported by any given driver. Sensors are registered with the kernel through sysmon_envsys(9) API. Consumption and monitoring of sensors from the userland is performed with the help of envstat utility through proplib(3) through ioctl(2) against the /dev/sysmon pseudo-device file, the powerd power management daemon that responds to kernel events by running scripts from /etc/powerd/scripts/, as well as third-party tools like symon and GKrellM from pkgsrc.
Some highlights are: a preview of metadata journaling for FFS file systems (known as WAPBL, Write Ahead Physical Block Logging)
"softdep" support is no longer available in FFS; use wapbl(4) logging instead.
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