Data striping
Encyclopedia
In computer data storage, data striping is the technique of segmenting logically sequential data, such as a file, in a way that accesses of sequential segments are made to different physical storage devices. Striping is useful when a processing device requests access to data more quickly than a storage devices can provide access. By performing segment accesses on multiple devices, multiple segments can be accessed concurrently. This provides more data access throughput, which avoids causing the processor to idly wait for data accesses. Striping is used across disk drives in RAID storage, network interfaces in Grid-oriented Storage
, and RAM
in some systems.
fashion from the beginning of the data sequence. This works well for streaming data, but subsequent random accesses will require knowledge of which device contains the data. If the data is stored such that the physical address of each data segment is assigned a 1-to-1 mapping to a particular device, the device to access each segment requested can be calculated from the address without knowing the offset of the data within the full sequence.
Other methods might be employed in which sequential segments are not stored on sequential devices. Such non-sequential interleaving can have benefits in some error correction
schemes.
Because different segments of data are kept on different storage devices, the failure of one device causes the corruption of the full data sequence. In effect, the failure rate of the array of storage devices is equal to the sum of the failure rate of each storage device. This disadvantage of striping can be overcome by the storage of redundant information, such as parity
, for the purpose of error correction. In such a system, the disadvantage is overcome at the cost of requiring extra storage.
s, such as Sybase
, and in certain RAID devices under software or hardware control, such as IBM
's RAMAC array subsystem. File systems of clusters also use striping. Oracle
Automatic Storage Management
allows ASM files to be either coarse or fine striped.
(LVM). The LVM system allows for the adjustment of coarseness of the striping pattern. LVM tools will allow implementation of data striping in conjunction with mirroring
; however, LVM1 will not allow adding additional disks to a striped Logical Volume (LV). This can be achieved with LVM2 using LVM2 format metadata.
.
Grid-oriented storage
Grid-oriented Storage is a dedicated data storage architecture which can be connected directly to a computational grid to support advanced data bank services and reservoirs for data that can be shared among multiple computers and end users on the grid....
, and RAM
Random-access memory
Random access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in...
in some systems.
Method
One method of striping is done by interleaving sequential segments on storage devices in a round-robinRound-robin
The term round-robin was originally used to describe a document signed by multiple parties in a circle to make it more difficult to determine the order in which it was signed, thus preventing a ringleader from being identified...
fashion from the beginning of the data sequence. This works well for streaming data, but subsequent random accesses will require knowledge of which device contains the data. If the data is stored such that the physical address of each data segment is assigned a 1-to-1 mapping to a particular device, the device to access each segment requested can be calculated from the address without knowing the offset of the data within the full sequence.
Other methods might be employed in which sequential segments are not stored on sequential devices. Such non-sequential interleaving can have benefits in some error correction
Error detection and correction
In information theory and coding theory with applications in computer science and telecommunication, error detection and correction or error control are techniques that enable reliable delivery of digital data over unreliable communication channels...
schemes.
Advantages and disadvantages
Advantages of striping include performance and throughput. Sequential time interleaving of data accesses allows the lesser data access throughput of each storage devices to be cumulatively multiplied by the number of storage devices employed. Increased throughput allows the data processing device to continue its work without interruption, and thereby finish its procedures more quickly. This is manifested in improved performance of the data processing.Because different segments of data are kept on different storage devices, the failure of one device causes the corruption of the full data sequence. In effect, the failure rate of the array of storage devices is equal to the sum of the failure rate of each storage device. This disadvantage of striping can be overcome by the storage of redundant information, such as parity
Parity bit
A parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code....
, for the purpose of error correction. In such a system, the disadvantage is overcome at the cost of requiring extra storage.
Wide Striping and Narrow Striping
Wide Striping occurs when chunks of data are spread across multiple arrays, possibly all the drives in the system. Narrow Striping occurs when the chunks of data are spread across the drives in a single array.Other Applications
Data striping is used in some modern databaseDatabase
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
s, such as Sybase
Sybase
Sybase, an SAP company, is an enterprise software and services company offering software to manage, analyze, and mobilize information, using relational databases, analytics and data warehousing solutions and mobile applications development platforms....
, and in certain RAID devices under software or hardware control, such as IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
's RAMAC array subsystem. File systems of clusters also use striping. Oracle
Oracle Corporation
Oracle Corporation is an American multinational computer technology corporation that specializes in developing and marketing hardware systems and enterprise software products – particularly database management systems...
Automatic Storage Management
Automatic Storage Management
Automatic Storage Management is a feature provided by Oracle Corporation within the Oracle Database from release Oracle 10g onwards. ASM aims to simplify the management of database files...
allows ASM files to be either coarse or fine striped.
Linux LVM
Data striping can also be achieved with Linux's Logical Volume ManagementLogical volume management
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...
(LVM). The LVM system allows for the adjustment of coarseness of the striping pattern. LVM tools will allow implementation of data striping in conjunction with mirroring
Disk mirroring
In data storage, disk mirroring or RAID1 is the replication of logical disk volumes onto separate physical hard disks in real time to ensure continuous availability...
; however, LVM1 will not allow adding additional disks to a striped Logical Volume (LV). This can be achieved with LVM2 using LVM2 format metadata.
RAID
In some RAID configurations (such as RAID-0) if one RAID disk fails, this file (and all other data), will be lost. In other RAID configurations (such as a RAID-5 with a parity drive), if one drive fails the data can be restored by using the other drives in the array. This is because RAID-5 uses parity error correcting redundancyRedundancy (information theory)
Redundancy in information theory is the number of bits used to transmit a message minus the number of bits of actual information in the message. Informally, it is the amount of wasted "space" used to transmit certain data...
.