Block (data storage)

A data block ( from the English data block) is limited, in some cases fixed number of bits or bytes that is treated as a transport unit. The block structure and the block elements correspond to the communication protocols in question.

• 2.1 Network
• 2.2 SCSI

Mass storage

Hard and floppy disks

Hard disks, and diskettes are in data blocks (short blocks or sectors mentioned ) divided. A data block is the smallest in an access readable or writable unit (now usually 512 bytes in size, since this variable cluster size of the original Unix file system corresponds; future 4096 bytes, since that's the minimum cluster size of modern operating systems, so a smaller data block size always would mean eight times as many writes). Each data block on a data carrier can be uniquely addressed, to which there are various methods - such as the LBA and the CHS addressing - are. LBA is the more modern method, for which - in contrast to the older CHS method - not the knowledge of disk geometry is required.

File systems organize data in general no longer at the lowest level of the data blocks, but at the next higher, the cluster ( Terminus in Windows; Terminus on Linux: blocks). Unlike the once common geometry-based addressing this method is also called block-based addressing.

Compact disc

For data storage, for example, on CD- ROM (Mode 1) 2048 bytes of user data are stored with additional error correction and synchronization data in a 2352 -byte block. This is a viable block size of 2 KiB, while reducing the bit error rate achieved by about ten thousand times.

Protocols

Network

In computer networks, the data blocks are referred to rather than the data packets. In most network protocols, the packet length is variable, however, there is often the minimum and / or maximum length of the packets. It must be large as a 10 - megabit Ethernet packet at least 64 bytes. Are to send less data, the packet is artificially by padding data (eg zeros ) increases, which are then ignored for the arrival of the packet.

SCSI

The SCSI protocol data blocks to send commands. It occurs in addition to SCSI drives on, inter alia, for drives with removable media ( CD and DVD drives) in your computer. There, data packets are referenced as packages that command, 10, 12 or 16 bytes in size.