block level

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block level

Reading and writing a disk at the physical level. The disk controller in every computer and server reads and writes the disks at the block level. In storage area networks (SANs), where the disks are in cabinets external to the server, read/write access is also at the block level.

Block Level Vs. File Level
An application accesses data by file name (logical), which is translated into block level (physical) for reading and writing by the operating system's file system.

Users always deal with data at the file level; however, database and network administrators may get involved at the block level, because they can stipulate where data are physically stored for performance issues.

Although a stand-alone unit with its own disks, a network attached storage (NAS) device has its own file system for file level access. Because a SAN uses block level access and has no file system with its associated overhead, a SAN is much faster than a NAS. See SAN, NAS and file system.

Remote Block Level Access
With IP storage, block level access can be extended via the IP protocol to remote locations. See SAN and IP storage.

Blocks Are Also Logical
Modern drives maintain their own tables of good and bad sectors and remap requests on the fly. As a result, the physical block reads and writes are translated by the drive into actual sector reads and writes, making the block access somewhat like a logical request, rather than 100% physical.

References in periodicals archive ?
Invitation to tender : Delivery, installation and commissioning of two block level storage systems according to capacity, features and qualities of the detail specification.
From the application point of view, SAN is similar to DAS, in terms of compatibility, during block level storage operations.
The company has now added the first volume status checks for EBS, which provides block level storage volumes for use with EC2 instances.
This iSCSI hardware optimized storage target is ideal for demanding solutions with block level storage needs.
iSCSI solutions require little more than the use of the Microsoft iSCSI initiator on a host server, a target iSCSI storage device and a Gigabit Ethernet switch to deliver block level storage over IP.
SAN or DAS block level storage devices in contrast cannot serve data to clients without the help of a server running a file system, because they don't include a file system.
However, to access high performance block level storage, users had to install an additional Fibre Channel storage area network (SAN) network by adding cards to their servers and an extra set of switches and target storage boxes.
With a cluster of SSCs, a pool of IP-addressable disks, and a flexible network interconnect, the resulting IP SAN not only offers fully virtualized block level storage, but provides the foundation to deliver storage services within the network infrastructure.
World-class engineering team with over 200 years of combined experience across clustered file systems, block level storage, backup facilities, iSCSI and open source
File virtualization (which can work in DAS and NAS as well as SAN), provides a virtual file system layer between files and block level storage.
It greatly reduces storage system complexities and simplifies designs of file level and block level storage appliances, intelligent switch implementations, high-end and mid-range RAID arrays, and intelligent host adapters and storage blades.
Direct-attached storage (DAS): DAS is still the most common storage architecture and provides the server-based block level storage that many databases require.