Spin-up refers to the process of a

hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magn ...

optical disc drive In computing, an optical disc drive is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only r ...

accelerating its

platters The Platters was an American vocal group formed in 1952. They are one of the most successful vocal groups of the early rock and roll era. Their distinctive sound bridges the pre-rock Tin Pan Alley tradition and the new burgeoning genre. The ac ...

or inserted

optical disc In computing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc that encodes binary data (bits) in the form of pits and lands on a special material, often aluminum, on one of its flat surfaces. ...

from a stopped state to an operational speed. The period of time taken by the drive to perform this process is referred to as its spin-up time, the average of which is reported by hard disks as a S.M.A.R.T. attribute. The required operational speed depends on the design of the disk drive. Typical speeds of hard disks have been 2400, 3600, 4200, 5400, 7200, 10000 and 15000

revolutions per minute Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensio ...

(RPM). Achieving such speeds can require a significant portion of the available power budget of a computer system, and so application of power to the disks must be carefully controlled. Operational speed of optical disc drives may vary depending on type of disc and mode of operation (see

Constant linear velocity In optical storage, constant linear velocity (CLV) is a qualifier for the rated speed of an optical disc drive, and may also be applied to the writing speed of recordable discs. CLV implies that the angular velocity (i.e. rpm) varies during an ...

). Spin-up of hard disks generally occurs at the very beginning of the computer boot process. However, most modern computers have the ability to stop a drive while the machine is already running as a means of

energy conservation Energy conservation is the effort to reduce wasteful energy consumption by using fewer energy services. This can be done by using energy more effectively (using less energy for continuous service) or changing one's behavior to use less service (f ...

noise reduction Noise reduction is the process of removing noise from a signal. Noise reduction techniques exist for audio and images. Noise reduction algorithms may distort the signal to some degree. Noise rejection is the ability of a circuit to isolate an un ...

. If a machine is running and requires access to a stopped drive, then a delay is incurred while the drive is spun up. It also depends on the type of mechanism used within. A drive in the process of being spun up needs more energy input than a drive that is already spinning at operation speeds, since more effort is required for the electric motor to accelerate the platters, as opposed to maintaining their speed.

Staggered spin-up

Staggered Spin-up (SSU) and Power-Up In Standby (PUIS) are features that can help control spin-up of multiple drives within a computer system or a disk subsystem. Both are defined in the ATA Specifications Standards. Staggered Spin-up (SSU) was introduced into SATA revision 2.5 in 2005. SSU allows a SATA host bus adapter to spin up hard drives in a sequential manner. Hard drive spin-up requires more power than maintaining operating rotational speed and staggering hard drive spin up in a multiple hard drive system reduces the maximum power needed for hard disk startup. The timing for sequential spin ups is set either by waiting a set amount of time for each disk to spin up, or by waiting for each disk to indicate that it is spun up and ready.

Power-up in standby In video games, a power-up is an object that adds temporary benefits or extra abilities to the player character as a game mechanic. This is in contrast to an item, which may or may not have a permanent benefit that can be used at any time chosen ...

(PUIS) (also called PM2Jumper Settings Info Sheet
) is used on some Serial ATA (SATA) and Parallel ATA (sometimes called PATA or IDE) hard disk drives. PUIS requires BIOS and/or driver support to use. When power is applied to the hard disk drive, the drive will not spin-up until a PUIS Spin-Up command is issued. The computer system

BIOS In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the ...

RAID controller A disk array controller is a device that manages the physical disk drives and presents them to the computer as logical units. It almost always implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides a ...

must issue the command to tell the drive(s) to spin-up before they can be accessed.{{cite web , title=Serial ATA Staggered Spin-Up , url=https://sata-io.org/system/files/member-downloads/Implementing%20Staggered%20Spin%20Up%20v1.pdf , website=sata-io.org , publisher=Intel , access-date=18 May 2022 PUIS can be enabled by tools such as

hdparm hdparm is a command line program for Linux to set and view ATA hard disk drive hardware parameters and test performance. It can set parameters such as drive caches, sleep mode, power management, acoustic management, and DMA settings. GParted ...

for drives which support this feature.

References

Booting Hard disk drives