2024-11-22

S.M.A.R.T

Glossary of Western Digital Hard Disk Drive (Letter S)

DATARECOVERYUNION.COM012 mins

S.M.A.R.T.
Self-monitoring, analysis, and reporting technology. A technology to assist users in preventing system down time due to hard drive failure; it attempts to predict hard drive failure before it occurs.

Safe Shutdown™
A WD-exclusive feature that ensures all data is transferred before shutting down the drive.

SAS
Serial Attached SCSI. A point-to-point serial interface that links controllers directly to hard drives. Unlike traditional parallel SCSI, SAS allows up to 128 devices of different sizes and types to be connected simultaneously with longer, thinner cables. SAS drives can also be hot-plugged.

SATA
Serial advanced technology attachment. A standard for connecting hard drives to computer systems, based on serial signaling technology. Its practical advantages over PATA (also known as EIDE) are longer and thinner cables for more efficient airflow within a form factor, fewer pin conductors for reduced electromagnetic interference, and lower signal voltage to minimize noise margin.

SCA-2
(Single Connector Attach) interface incorporates a grounding contact, blindmate connector, direct plug misalignment tolerance, The number of errors of a given type that occur when reading a specified number of bits. Protection, hot swap capability, and backplane connector options for SCSI devices. SCA-2 is commonly called the 80-pin SCSI connector.

SCAM
SCSI configure automatically. Allows users to attach SCSI devices without worrying about configuration options.

SCSI
Small computer system interface. An interface between a computer and peripheral controllers, commonly used in enterprise computing and Macintosh systems. Pronounced scuzzy.

SCSI device
A host computer adapter, peripheral controller, or intelligent peripheral that can be attached to a SCSI bus.

sector
A 512-byte packet of data. This is the smallest amount of data that can be read from or written to a drive from a host interface.

sector slipping
A technique used to push down defective sector sites during a format or reassignment operation to maintain sequential order of the data. Spares are located throughout the disk for this purpose.

SecureConnect™
WD’s SATA cable connection system designed to provide a stable, secure attachment between a hard drive and a cable.

SecurePark™
Parks the recording heads off the disk surface during spin up, spin down and when the drive is off. This ensures the recording head never touches the disk surface resulting in improved long term reliability due to less head wear and improved shock tolerance.

seek
The movement of read/write heads to a specified location. The actuator moves heads to the cylinder containing the track and sector of stored data.

seek time
A measure (in milliseconds) of how fast a hard drive can move its read/write heads to a specific location.

sequential access
The reading or writing of data in a sequential order as opposed to random access. Magnetic tape drives store data in sequential blocks.

server
A computer used primarily to store data, providing access to shared resources. Usually contains a network operating system.

servo burst
Provides positioning information to the actuator arm, found at equal intervals on each disk surface (embedded servo) or on an entire surface (dedicated servo).

share
A folder that can be used to organize and store files on a network storage system. Shares can be shared with everyone (public) or with selected users on your network (private).

Shock Guard™
WD technology to protect the drive mechanics and delicate platter surface from shocks, both when it’s in use and when it’s not.

ShockShield™
WD packaging that provides double protection from rough handling and static damage. A protective wrapping that consists of a static protection envelope securely packed inside a plastic case.

SilkStream™
WD AV feature that provides for smooth, continuous digital video playback of multiple simultaneous hard drive streams.

single-ended SCSI
The standard electrical interface for SCSI. Single-ended means an interface with one signal and one corresponding ground line for each SCSI signal. Used primarily in applications requiring cable lengths under 19 feet (6 meters).

Slave
The secondary drive in a dual-drive configuration.

SmartPower™
Intelligent drive management system that automatically powers a device on and off with the computer.

SMB
Server Message Block. File-sharing protocol for Windows platform that allows users to access shares through My Network Places. Mac OS X or later also supports the SMB protocol.

SMTP
Simple Mail Transfer Protocol. Standard for transferring e-mail across the Internet.

soft error
An error that is not repeated when the same location is re-read.

soft reset
ATA reset type in which the drive resets the interface circuitry according to the Set Features command requirement.

soft sectored
A technique that allows a controller to determine the beginning of a sector by reading format information from a disk.

SoftSeek™
A WD algorithm used with WhisperDrive™ technology to deliver the quietest 2.5-inch hard drive on the market.

sound power
A value measured using 8-12 microphones which represents the sound level emitted from the entire hemispherical area surrounding the drive. Because sound power more closely corresponds to the sound level detected by the human ear, it is used as the industry standard for measuring hard drive acoustics.

sound pressure
A value representing the sound level emitted by a hard drive from a single point. Only one microphone is used to measure sound pressure.

spanned
Combination of drives in a linear fashion to create one large logical volume. A spanned drive is like a single, bigger drive, in that files written to the volume earlier go at the "beginning" of the volume, on the first physical drive. If one of the drives fails, all data is lost.

SPC
SCSI Primary Commands.

spindle
The center, rod-like axle on which disks are mounted.

spindle motor
A motor that rotates a spindle and ultimately the disks.

spindle speed
See RPM.

spindle synchronization
In multiple-drive systems, a feature that causes SCSI hard drives to rotate to the same address location at the same time.

SSA

SSC
Spread Spectrum Clocking. Feature that controls electromagnetic interference output in hard drives.

SSH
Secure Shell. A network protocol that uses encryption and authentication keys to enable two devices on the network to exchange data securely.

SSL
Secure Socket Layer. A protocol that provides authentication and encryption services between a web server and a web browser.

StableTrac™
The motor shaft of the hard drive is secured at both ends to reduce system-induced vibration and stabilize platters for accurate tracking during read and write operations.

storage capacity
The amount of data that can be stored on a hard drive.

streaming media
Media such as audio, video, and photos that are constantly received while being delivered by a streaming provider.

striping
The spread of data over multiple hard drives to improve performance. See also RAID 0.

structure-borne acoustics
When mounted in a digital device, the hard drive generates additional noise as a result of vibration. This type of noise, caused by the hard drive’s proximity to other system components, is referred to as structure-borne acoustics.

subsystem
A secondary or component part of a system, as a hard drive is a subsystem of a personal computer.

surface
The top or the bottom side of a platter coated with a magnetic material required to record data. A platter may use one or both surfaces to store data.

synchronous transmission
Transmission in which the sending and receiving devices operate continuously at the same frequency and are held in a desired phase relationship by a correction device.

system files
The files required to run an operating system.

system integrator
An independent professional who specifies and provides the necessary combinations of hardware and software in response to end user needs.

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Basic Information of Hard Disk Drive (Part I)

DATARECOVERYUNION.COM03 mins

Modern hard disks feature an area that contains information that the CPU on the HDD logic board uses to operate the drive. The area is called the “system area” (“SA”). This area contains for example the drive ‘microcode’ (a.k.a. firmware), HDD Configuration Tables, Defect sector tables, SMART information, Security info (drive passwords etc), Disk ID info and more. These categories of information are called ‘modules’. So the SA contains a module for the firmware code, a module for the SMART info etc.

The SA is stored on ‘negative cylinders’ of the HDD and therefore is not accessible by normal read commands. However, the area can be accessed with other ATA commands. An example of a (more or less) ‘standard’ ATA command that can access info on the SA is the ‘download microcode’ ATA command that can be used to update information in the firmware code module. However, most of the commands that can be used to access the SA are vendor specific. Since vendors (obviously) don’t want users to mess around with the SA, these commands are generally not made public. However, these commands can be deduced by, for example, reverse engineering the firmware code itself.

This reverse engineering has been done and led to development of tools that can issue these (vendor specific) ATA commands and can read/write almost all sectors in the SA. One example of such tool is PC3000 (‘PC3K’). A tool like this contains tables per HDD model, containing these vendor specific ATA commands and also tables with sector numbers on which the different modules are stored, also per HDD model. SA Sector numbers are counted in “UBA’s”. For example, one specific HDD might use UBA 4 to store the ‘DISK ID’ module, where another HDD model might use another sector for this module.

So in short, to create a tool that can read/write data in the SA, you need to:

1) know (and understand) the (vendor-) specific ATA commands that can be used to access this area and

2) know on which UBA sector the specific modules are stored.

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Hard Drive Technology

DATARECOVERYUNION.COM03 mins

Hard disk storage manufacturers have been always working to improve the technology. Storage space, data transfer rates, and internal error checking have been the guiding principles of hard drive technology. Data Recovery companies work hard to maintain their capabilities to be compatible with these emerging technologies so that they can provide the best hard drive recovery for their client’s data. What are some of the advancements in hard disk storage devices? What are some common data loss scenarios with hard disk storage? This document will help answer these questions and more. Let’s begin with looking at the inner workings of the hard disk itself.

Hard Drives — Technology in Action

Types of common failures include:

As we know, hard drives are a combination of sophisticated electronic and mechanical systems that incorporate a number of specialized motors and electro-mechanical components to read and write data.

Hard drive technology has substantially advanced in the past 10 years. In fact, hard drives are designed to manage themselves in addition to reading and writing data. Hard drives today use a number of algorithms to verify data on the drive and also maintains a ‘Defect Management’ list internally that constantly monitors their own health and performance. If a sector is beginning to fail, the hard drive’s electronics will remove that sector from use. In addition to this, S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology) circuitry has been incorporated on many hard drives and is used to monitor all of the internal systems.

Despite these safeguards, hard drives can fail. There can be a number of reasons for hard drive failure, for instance physical damage can result when the hard drive or case is jarred while operating or even when powered off. Power spikes or fluctuations can damage the electronics or corrupt the data on the drive. Internal mechanical parts can seize up due to high temperatures if the drive does not have enough airflow to keep the unit cool.

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Technologies used for maintaining HDD reliability

DATARECOVERYUNION.COM04 mins

With all the complications HDD manufacturers are constantly trying to make user data storage more reliable. To accomplish that they use various methods and technologies in their drives.

Figure 5. Control circuit of spindel of HDD (family WDAC 32500 and WDAC 33100)
S.M.A.R.T. (abbreviated Self-Monitoring, Analysis, and Reporting Technology) is intended to inform hard drive users about the status of its main parameters. Many motherboard BIOSes support analysis of those parameters at computer power-up and if some critical parameter exceeds its emergency limit an informational message is displayed during computer start-up. Of course, it does not mean that the drive will stop functioning, but the user should take some steps in that situation, for example, prepare a backup copy of valuable data. If computer BIOS does not contain an analyzer of S.M.A.R.T. attributes you can use an external diagnostic utility launched from within the operating system. The list of such utilities includes, for instance, SMART Vision available from http://www.acelab.ru/products/pc/traning.html.

For greater reliability practically all drives use a technology, which allows hiding and relocation of occurring defects immediately during operation. Some peculiarities of its implementation may vary with different drive models; however, they are all based upon the same principle. If the operating system attempts to access a sector, which cannot be read or written to, then the drive will replace it if possible (if there is sufficient reserved space) with a sector from the reserved zone (assign). The table of thus substituted sectors is stored in drive firmware zone and the drive loads it to controller ROM at power-up.

Impact sensors found in all drives also belong to technologies used for protection against malfunctions. It is a piezoelectric sensor producing an electric pulse at mechanical shock. Filtering of sensor pulses allows identification of obvious impacts. When a drive detects shock action, it parks magnetic heads. One peculiarity of impact sensor installation is the angle of its mounting relative to front case line. It is equal to 45O.

In recent models manufacturers have began to use widely temperature sensors in PCB and heads’ block. Temperature information is monitored by drive processor and the drive stops operation if the allowed value is exceeded. In some drive models temperature is output as S.M.A.R.T. attribute value and there are programs (usually available from the web pages of HDD manufacturers) which allow viewing it.

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