Disk data format

Last updated

The SNIA common RAID disk data format (DDF) defines a standard data structure describing how data is formatted across disks in a RAID group. The DDF structure allows a basic level of interoperability between different suppliers of RAID technology. The common RAID DDF structure benefits storage users by enabling in-place data migration or recovery after controller failure using systems from different vendors. [1]

DDF is an external metadata format that is compatible with the mdraid subsystem in the Linux kernel. The mdadm command-line utility is a part of the mdraid subsystem. [2]

Related Research Articles

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 its default file system.

RAID is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both. This is in contrast to the previous concept of highly reliable mainframe disk drives referred to as "single large expensive disk" (SLED).

In computer storage, logical volume management or LVM provides a method of allocating space on mass-storage devices that is more flexible than conventional partitioning schemes to store volumes. In particular, a volume manager can concatenate, stripe together or otherwise combine partitions into larger virtual partitions that administrators can re-size or move, potentially without interrupting system use.

<span class="mw-page-title-main">Data striping</span>

In computer data storage, data striping is the technique of segmenting logically sequential data, such as a file, so that consecutive segments are stored on different physical storage devices.

Sistina Software was a US company that focused on storage solutions designed around a Linux platform. It originated in the University of Minnesota.

In computing, the Global File System 2 or GFS2 is a shared-disk file system for Linux computer clusters. GFS2 allows all members of a cluster to have direct concurrent access to the same shared block storage, in contrast to distributed file systems which distribute data throughout the cluster. GFS2 can also be used as a local file system on a single computer.

In Linux, Logical Volume Manager (LVM) is a device mapper framework that provides logical volume management for the Linux kernel. Most modern Linux distributions are LVM-aware to the point of being able to have their root file systems on a logical volume.

The device mapper is a framework provided by the Linux kernel for mapping physical block devices onto higher-level virtual block devices. It forms the foundation of the logical volume manager (LVM), software RAIDs and dm-crypt disk encryption, and offers additional features such as file system snapshots.

The following tables compare general and technical information for a number of file systems.

ext4 is a journaling file system for Linux, developed as the successor to ext3.

The Linux Unified Key Setup (LUKS) is a disk encryption specification created by Clemens Fruhwirth in 2004 and was originally intended for Linux.

In computer storage, the standard RAID levels comprise a basic set of RAID configurations that employ the techniques of striping, mirroring, or parity to create large reliable data stores from multiple general-purpose computer hard disk drives (HDDs). The most common types are RAID 0 (striping), RAID 1 (mirroring) and its variants, RAID 5, and RAID 6. Multiple RAID levels can also be combined or nested, for instance RAID 10 or RAID 01. RAID levels and their associated data formats are standardized by the Storage Networking Industry Association (SNIA) in the Common RAID Disk Drive Format (DDF) standard. The numerical values only serve as identifiers and do not signify performance, reliability, generation, or any other metric.

mdadm is a Linux utility used to manage and monitor software RAID devices. It is used in modern Linux distributions in place of older software RAID utilities such as raidtools2 or raidtools.

The multi-stage booting process of Linux is in many ways similar to the BSD and other Unix-style boot processes, from which it derives.

dm-crypt is a transparent block device encryption subsystem in Linux kernel versions 2.6 and later and in DragonFly BSD. It is part of the device mapper (dm) infrastructure, and uses cryptographic routines from the kernel's Crypto API. Unlike its predecessor cryptoloop, dm-crypt was designed to support advanced modes of operation, such as XTS, LRW and ESSIV, in order to avoid watermarking attacks. In addition to that, dm-crypt addresses some reliability problems of cryptoloop.

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".

<span class="mw-page-title-main">Noop scheduler</span> Simple I/O scheduler for the Linux kernel

The NOOP scheduler is the simplest I/O scheduler for the Linux kernel. This scheduler was developed by Jens Axboe.

A trim command allows an operating system to inform a solid-state drive (SSD) which blocks of data are no longer considered to be 'in use' and therefore can be erased internally.

Shingled magnetic recording (SMR) is a magnetic storage data recording technology used in hard disk drives (HDDs) to increase storage density and overall per-drive storage capacity. Conventional hard disk drives record data by writing non-overlapping magnetic tracks parallel to each other, while shingled recording writes new tracks that overlap part of the previously written magnetic track, leaving the previous track narrower and allowing higher track density. Thus, the tracks partially overlap similar to roof shingles. This approach was selected because, if the writing head is made too narrow, it cannot provide the very high fields required in the recording layer of the disk.

References

  1. "Common RAID Disk Data Format (DDF)". SNIA.org. Storage Networking Industry Association.
  2. "Chapter 21. Managing RAID Red Hat Enterprise Linux 8". Red Hat Customer Portal. Retrieved 2023-01-06.