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A block, a contiguous number of bytes, is the minimum unit of storage that is read from and written to a disk by a disk driver.The earliest disk drives had fixed block sizes (e.g. the IBM 350 disk storage unit (of the late 1950s) block size was 100 six-bit characters) but starting with the 1301 [8] IBM marketed subsystems that featured variable block sizes: a particular track could have blocks ...
When using Advanced Format drives with legacy operating systems, it is important to realign the disk drive using software provided by the hard disk manufacturer. Disk realignment is necessary to avoid a performance degrading condition known as cluster straddling where a shifted partition causes filesystem clusters to span partial physical disk ...
Subsequently, the first drive (containing a CTL-I controller) in a string of drives was designated by IBM as an A-unit. [5] The drives within an A-unit and all other drives in a string had interfaces similar to the early interfaces, above. A-units connected to IBM Directors or integrated attachments.
Historically, most SSDs used buses such as SATA, [19] SAS, [20] [21] or Fibre Channel for interfacing with the rest of a computer system. Since SSDs became available in mass markets, SATA has become the most typical way for connecting SSDs in personal computers; however, SATA was designed primarily for interfacing with mechanical hard disk drives (HDDs), and it became increasingly inadequate ...
For most disks, each sector stores a fixed amount of user-accessible data, traditionally 512 bytes for hard disk drives (HDDs), and 2048 bytes for CD-ROMs, DVD-ROMs and BD-ROMs. [1] Newer HDDs and SSDs use 4096 byte (4 KiB) sectors, which are known as the Advanced Format (AF). The sector is the minimum storage unit of a hard drive. [2]
Non-volatile memory (NVM) or non-volatile storage is a type of computer memory that can retain stored information even after power is removed. In contrast, volatile memory needs constant power in order to retain data.
The specification was released on December 20, 2011, as a mechanism for providing PCI Express connections to SSDs for the enterprise market. Goals included being usable in existing 2.5" and 3.5" form factors, to be hot swappable and to allow legacy SAS and SATA drives to be mixed using the same connector family. [2]
Non-volatile random-access memory (NVRAM) is random-access memory that retains data without applied power. This is in contrast to dynamic random-access memory (DRAM) and static random-access memory (SRAM), which both maintain data only for as long as power is applied, or forms of sequential-access memory such as magnetic tape, which cannot be randomly accessed but which retains data ...