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Glossary of Western Digital Hard Disk Drive (Letter M)

August 14th, 2010

imageMagnetic flux
A pattern of magnetic pole directions of bits written on a disk.

Master
The primary drive in a dual-drive configuration. A Master drive by itself (with no Slave) is called a single drive.

MB
Megabyte. WD defines a megabyte as 1,000,000 (one million) bytes.

mechanical latency
A time period, including both seek time and rotational latency. Mechanical latencies are the main hindrance to higher performance in hard drives and are one hundred times greater than electronic (non-mechanical) latencies associated with data transfers. See also rotational latency and seek time.

media
In hard drives, the disks and their magnetic coatings. Sometimes refers only to the coating material.

memory
A device or system capable of storing and retrieving data.

MFM
Multiple frequency modulation. A method of encoding analog signals into magnetic pulses or bits.

MioNet®
WD’s remote computer access service. Adding MioNet to your home or work computer provides secure and instant access from any PC in the world back to your computer. You can use your applications and access and share files on your computer or storage device from anywhere.

mirroring
The process of generating an exact copy of saved data from one drive to another drive within a RAID 1 system. Each drive can be accessed and read separately. A mirrored drive can be removed from a system while the other drive(s) are still active. See also RAID 1.

MP3
MPEG-audio layer 3. A digital audio coding scheme for distributing music over the Internet.

MR head
Magnetoresistive head. MR heads were developed to increase areal density and improve drive performance. These heads use an inductive element for writing data and a separate magnetoresistive element for reading data, rather than traditional inductive thin-film, read/write heads. The read element has a magnetically sensitive material that detects data recorded on the magnetic disk surface. MR head construction results in a stronger signal than that produced by inductive thin-film, read/write heads, which allows reading higher areal density data.

MTBF
Mean time between failures. The average time (expressed in hours) that a component works without failure. This time is calculated by dividing the total number of operating hours observed by the total number of failures. Also, the length of time a user may reasonably expect a device or system to work before an incapacitating fault occurs.

MTTR
Mean time to repair. The average time it takes to repair a drive in the field. Only major subassemblies (the PCB, sealed housing, etc.) are changed in the field; component level repairs are not performed in the field.

multimedia
A simultaneous presentation of data in more than one form, such as by means of both video and audio.

multi-user
A system in information technology that enables more than one user to access data at the same time.

My Book 3.0
Trade name for WD’s initial line of USB 3.0 external hard drives.

My Book®
Trade name for WD external hard drives with a book-shaped enclosure.

My DVR Expander™ eSATA Edition™
WD external device that adds additional storage capacity to a DVR with an enabled eSATA port.

My DVR Expander™ USB Edition™
WD external device that adds additional storage capacity to a DVR with an enabled USB port.

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