Patent Publication Number: US-2023142716-A1

Title: Dual spindle motor hard disk drive

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to commonly-owned pending U.S. Provisional Patent Application No. 63/277,108 filed on Nov. 8, 2021, the entire content of which is incorporated by reference for all purposes as if fully set forth herein. 
    
    
     FIELD OF EMBODIMENTS 
     Embodiments of the invention may relate generally to data storage devices, and particularly to a hard disk drive having two disk spindle motors. 
     BACKGROUND 
     A hard disk drive (HDD) is a non-volatile storage device that is housed in a protective enclosure and stores digitally encoded data on one or more circular disks having magnetic surfaces. When an HDD is in operation, each magnetic-recording disk is rapidly rotated by a spindle system. Data is read from and written to a magnetic-recording disk using a read-write head (or “transducer”) housed in a slider that is positioned over a specific location of a disk by an actuator. A read-write head makes use of magnetic fields to write data to and read data from the surface of a magnetic-recording disk. A write head works by using the current flowing through its coil to produce a magnetic field. Electrical pulses are sent to the write head, with different patterns of positive and negative currents. The current in the coil of the write head produces a localized magnetic field across the gap between the head and the magnetic-recording disk, which in turn magnetizes a small area on the recording medium. 
     Increasing areal density (a measure of the quantity of information bits that can be stored on a given area of disk surface) is one of the on-going goals of hard disk drive technology evolution. In one form, this goal manifests in the type of high-capacity HDDs that are especially attractive in the context of enterprise, cloud computing/storage, and data center environments. However, the performance of high-capacity HDDs has not necessarily scaled up commensurately with the increases in capacity. This has led to the need to develop and implement various means to increase high-capacity HDD performance. 
     In recent years the growth in areal density in HDDs has not kept pace with the trends of years past. This has shifted the burden on the mechanics to boost capacity increases by increasing the number of disks within the prescribed form factor. As these HDDs are primarily used for near line storage in data centers in hyper-scale environments, the performance of these high-capacity drives also has to satisfy the IOPs (Input/Output Operations Per Second) density requirements (in some instances, similarly referred to as IOPs/TB) to minimize latency. This demand has led to a shift to multiple actuators for providing parallel access to data. 
     Any approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
         FIG.  1    is a plan view illustrating a hard disk drive (HDD), according to an embodiment; 
         FIG.  2    is a cross-sectional side view illustrating a dual-actuator shared shaft actuator system, according to an embodiment; 
         FIG.  3    is a side view diagram illustrating a dual spindle motor configuration for a hard disk drive, according to an embodiment; and 
         FIG.  4    is a top view diagram illustrating top and bottom portions of the dual spindle motor configuration of  FIG.  3   , according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Generally, approaches to a dual spindle motor hard disk drive are described. The term “spindle motor” is used herein in reference to a recording disk media spindle motor assembly configured to spin the disk media for data read and write operations, such as the drive motor described in reference to  FIG.  1   . In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention described herein. It will be apparent, however, that the embodiments of the invention described herein may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the embodiments of the invention described herein. 
     INTRODUCTION 
     Terminology 
     References herein to “an embodiment”, “one embodiment”, and the like, are intended to mean that the particular feature, structure, or characteristic being described is included in at least one embodiment of the invention. However, instances of such phrases do not necessarily all refer to the same embodiment, 
     The term “substantially” will be understood to describe a feature that is largely or nearly structured, configured, dimensioned, etc., but with which manufacturing tolerances and the like may in practice result in a situation in which the structure, configuration, dimension, etc. is not always or necessarily precisely as stated. For example, describing a structure as “substantially vertical” would assign that term its plain meaning, such that the sidewall is vertical for all practical purposes but may not be precisely at 90 degrees throughout. 
     While terms such as “optimal”, “optimize”, “minimal”, “minimize”, “maximal”, “maximize”, and the like may not have certain values associated therewith, if such terms are used herein the intent is that one of ordinary skill in the art would understand such terms to include affecting a value, parameter, metric, and the like in a beneficial direction consistent with the totality of this disclosure. For example, describing a value of something as “minimal” does not require that the value actually be equal to some theoretical minimum (e.g., zero), but should be understood in a practical sense in that a corresponding goal would be to move the value in a beneficial direction toward a theoretical minimum. 
     Context 
     Recall the observation that the performance of high-capacity HDDs has not scaled up commensurately with increases in storage capacity. The high latencies of large capacity HDDs in a clustered environment, such as in data centers with multiple clustered nodes, results in a bottleneck due to slower access to stored data. The pressure to increase the performance (e.g., TOPS) by reducing the latencies for data operations of high-capacity HDDs has become even stronger as capacities of HDDs continue to increase. One possible approach to increasing HDD performance is the implementation of multi-actuator systems, in which multiple independently operating actuators are assembled onto a single shared pivot shaft in order to independently and concurrently read from and/or write to multiple recording disks of a disk stack. 
       FIG.  2    is a cross-sectional side view illustrating a dual-actuator shared shaft actuator system, according to an embodiment. Actuator system  200 , generalized, comprises a shaft  202  having a bore  203  at least partially therethrough. According to an embodiment, the shaft  202  is utilized as a pivot shaft, or part of an actuator pivot assembly or shared shaft assembly, for multiple actuators constituent to a multi-actuator shared shaft data storage device such as a hard disk drive (HDD). As such, actuator system  200  comprises the shaft  202 , around which a first or lower rotary actuator assembly  204  (e.g., a voice coil actuator, and including a carriage  204   a , such as carriage  134  of  FIG.  1   ) is rotatably coupled at a first location of shaft  202 , with a lower bearing assembly  206  interposed therebetween, and around which a second upper rotary actuator assembly  205  (e.g., a voice coil actuator, and including a carriage  205   a , such as carriage  134  of  FIG.  1   ) is rotatably coupled at a second location of shaft  202 , with an upper bearing assembly  207  interposed therebetween. Alternatively and according to an embodiment, the functionality of the shaft  202  utilized as a pivot shaft may be implemented with separate shafts, e.g., one for each respective actuator assembly  204 ,  205 , rather than a shared shaft assembly such as shaft  202 . This could provide for decoupling of undesired structural dynamics associated with the independent operation of multiple actuator assemblies, such as actuator assembly  204  and actuator assembly  205 , mounted on a single shared shaft. 
     “Clamshell” Dual Spindle Motor Configuration 
     Described herein are approaches to a so-called “clamshell” dual spindle motor design for use in a hard disk drive (HDD), such as data storage device similar to the hard disk drive of  FIG.  1   .  FIG.  3    is a side view diagram illustrating a dual spindle motor configuration for a hard disk drive, according to an embodiment, and  FIG.  4    is a top view diagram illustrating top and bottom portions of the dual spindle motor configuration of  FIG.  3   , according to an embodiment. Dual spindle motor hard disk drive  300  (“HDD  300 ”) is configured as what is referred to as a clamshell HDD  300 , in that it comprises two separate portions or parts in which their open sides are coupled together face-to-face, similar to the shells of a clam. However, here, the two portions are not necessarily hinged as with a traditional clamshell. In some embodiments, the two portions may each be a motor base assembly in which a spindle motor is integrated within a base casting, with supportive wiring and mechanical features such as feed-throughs and mounting/sealing structures. In some embodiments, the top portion and the bottom portion may be the same or substantially the same, or have different construction and/or configuration to accommodate various needs such as wiring routing, mechanical dynamics, sealing optimizations, etc. 
     HDD  300  comprises a first (e.g., top) portion  302  that comprises a first spindle motor  304  and a plurality of (i.e., multiple) first disk media  306  rotatably mounted on the first spindle motor  304 . First portion  302  further comprises a first enclosure  308  having an open side  308   a  and a closed side  308   b . HDD  300  further and similarly comprises a second (e.g., bottom) portion  352  that comprises a second spindle motor  354  and a plurality of (i.e., multiple) second disk media  356  rotatably mounted on the second spindle motor  354 . Second portion  352  further comprises a second enclosure  358  having an open side  358   a  and a closed side  358   b . The first spindle motor  304  is mounted on or coupled with the first enclosure  308  of the first portion  302  and the second spindle motor  354  is mounted on or coupled with an opposing second enclosure  358  of the second portion  352 . As depicted, the first portion  302  and the second portion  352  are coupled together such that the open side  308   a  of the first enclosure  308  mates with the open side  358   a  of the second enclosure  358 , thus forming the clamshell configuration having coaxial first and second spindle motors  304 ,  354 . First portion  302  and second portion  352  may be coupled together with fasteners, or via welding, and the like, with one or more seal  309 ,  359  (e.g., a gasket seal) therebetween. The clamshell configuration of HDD  300  may enable the use of a significant amount of existing manufacturing infrastructure, such as tooling and processes, thus providing a feasible and practical dual spindle motor design. 
     According to an embodiment and as depicted in  FIG.  3   , the first and second spindle motors  304 ,  354  have separate and independent but coaxial central shafts  305  and  355 , respectively. However, implementation of a shared central shaft that is shared by the first and second spindle motors  304 ,  354  is contemplated. Regardless, independent central shafts  305 ,  355  or not, each of the first spindle motor  304  and the second spindle motor  354  is configured for rotating the respective first and second disk media  306 ,  356  independent of the other, some operational control of which is described in more detail elsewhere herein. Furthermore and as depicted in  FIG.  4   , the first and second spindle motors  304 ,  354  are configured to rotate in opposite directions (clockwise versus counter-clockwise) relative to or from the perspective of the open side  308   a ,  358   a  of the respective first and second enclosures  308 ,  358 . Hence, when the enclosures  308 ,  358  are coupled together in a clamshell configuration, the first and second spindle motors  304 ,  354  are then configured to rotate in the same direction, i.e., as one of the portions such as the top or first portion  302  is now upside-down with its open side  308   a  now facing downward in the context of  FIG.  3   . 
     The second portion  352  further comprises a second plurality of head sliders each housing a read-write transducer (not visible here; see, e.g., slider  110   b  that includes a magnetic read-write head  110   a  of  FIG.  1   ) configured to read from and to write to a respective disk medium of the second disk media  356  and a second actuator  360  configured for moving the first plurality of head sliders to access portions of the second disk media  356 . According to an embodiment, the second portion  352  further comprises a first plurality of head sliders each housing a read-write transducer (not visible here; see, e.g., slider  110   b  that includes a magnetic read-write head  110   a  of  FIG.  1   ) configured to read from and to write to a respective disk medium of the first disk media  306  and a first actuator  310  configured for moving the first plurality of head sliders to access portions of the first disk media  306 . Thus, according to this embodiment, while each of the first and second portions  302 ,  352  comprise a respective disk spindle motor  304 ,  354  on a respective central shaft  305 ,  355  and to which the respective first and second disk media  306 ,  356  are clamped or otherwise coupled, the bottom or second portion  352  of HDD  300  houses and supports both the actuators  310 ,  360  and head sliders  110   a / 110   b  operationally corresponding to both the first and second disk media  306 ,  356 . According to an embodiment and as depicted in  FIG.  3   , the first and second actuators  310 ,  360  share a common central shaft  362 , while each is configured to operate independently of the other on the respective disk media  306 ,  356 . However, implementation of split or independent central shafts for each respective actuator  310 ,  360  is contemplated. 
     While the number of recording disks in disk media  306  and  356  (and the respective supporting heads/sliders) are depicted as equal in  FIG.  3   , the number of disks in each respective stack of disk media  306 ,  356  may be different or unequal in various embodiments. Furthermore, various supportive mechanical and electrical structures and arrangements (e.g., motor size) can be tailored to match the different numbers of media in the respective portions first and second portions  302 ,  352 . 
     According to an embodiment, the second portion  352  further comprises a printed circuit board assembly  364  (“PCBA 364”) comprising spindle motor drive(r) electronics (not visible here) for providing electrical signals to the first and second spindle motors  304 ,  354  to enable them to spin to provide torque to the spindle which is in turn transmitted to the respective first and second disk media  306 ,  356  affixed to each spindle, and an electrical cable assembly  366  (such as a flexible cable assembly, or “FCA  366 ”) coupled with the spindle motor driver. Here, the second spindle motor  354  of the bottom or second portion  352  may be electrically coupled to the driver electronics as typical and known in the art, while the FCA  366  is routed to and further electrically couples the first spindle motor  304  of the first portion  302  to the driver electronics. Thus, prior to coupling the first portion  302  with the second portion  352 , the FCA  366  needs to be electrically connected with the first spindle motor  304  of the first portion  302  of the multiple spindle motor HDD  300 . 
     Operational Control of a Dual Spindle Motor Hard Disk Drive 
     Processing, functions, procedures, actions, method steps, and the like that are described herein may include enactment by execution of one or more sequences of one or more instructions stored in one or more memory units and which, when executed by one or more processors, cause such performance. Referenced controllers may be embodied in any form of and/or combination of software, hardware, and firmware. An electronic controller in this context typically includes circuitry such as one or more processors for executing instructions, and may be implemented as a System On a Chip (SoC) electronic circuitry, which may include a memory, a microcontroller, a Digital Signal Processor (DSP), an application-specific integrated circuit (ASIC), a Field Programmable Gate Array (FPGA), hard-wired logic, analog circuitry and/or a combination thereof, for non-limiting examples. Firmware, which may be stored in controller memory, includes computer-executable instructions for execution by the controller in operating HDD  300  ( FIG.  3   ). 
     As introduced, one approach to increasing HDD performance is through the implementation of multi-actuator systems in which multiple independently operating actuators in order to independently and concurrently read from and/or write to multiple recording disks of a disk stack. A dual-actuator or split actuator HDD involves use of dual VCMs (voice coil motor) in order to increase the performance. Furthermore, with a “split single actuator” configuration, the use of only one actuator actively at a time is contemplated. By adding a second motor within the drive and dividing the disks among the motors, finer control over the usage and power consumption of each disk stack is enabled. That is, use of a dual spindle motor design such as dual spindle motor HDD  300  ( FIG.  3   ) can address the increasing power challenges due to increased activity on the media by way of increasing performance using split actuator designs. 
     Stated otherwise, power consumption can be greatly reduced because part of the drive is not being used at any given time and, therefore, each set of spindle motor and actuator may be independently controlled to operate in a low-power or idle mode or turned off altogether to save power. For example, setting part of the drive into a lower-powered idle mode by parking the actuator and shutting down some of the electronics, while the remaining electronics stay on for any active workloads, may be enabled with HDD  300 . Thus, according to an embodiment an electronic controller may be configured to set one of the first and second actuators  310 ,  360  ( FIGS.  3 - 4   ) and corresponding first or second spindle motors  304 ,  354  ( FIGS.  3 - 4   ) to a low-power (e.g., relative to fully operational power needs) idle mode, e.g., whereby the spindle motor is spinning at a low rotational speed, while the other of the first and second actuators  310 ,  360  and corresponding first or second spindle motors  304 ,  354  is simultaneously set to an active (e.g., fully operational) mode. Similarly and according to an embodiment, the electronic controller may be configured to set one of the first and second actuators  310 ,  360  and corresponding first or second spindle motors  304 ,  354  to a power-off mode, e.g., whereby the spindle motor is not powered to spin at all (and the corresponding actuator may be parked and corresponding electronics powered down), while the other of the first and second actuators  310 ,  360  and corresponding first or second spindle motors  304 ,  354  is simultaneously set to an active (e.g., fully operational) mode. Still further and according to an embodiment, the electronic controller may be configured to set one of the first or second spindle motors  304 ,  354  to spin at a first rotational speed (or RPM, revolutions per minute) while the other of the first and second spindle motors  304 ,  354  is simultaneously set to spin at a different second rotational speed. An example application of such a technique would be for surveillance products where the vast majority of the I/O (input-output) activities are sequential WRITE operations, whereby these operations can generally be performed by one half of the HDD  300  while the other half of HDD  300  can stay idle (e.g., spin at a lower speed, or no spin) to reduce power and temperature. 
     With independent control of multiple or dual spindle motors such as with HDD  300 , incoming data may be first stored on half of the drive, such as on the first disk media  306  served by the first spindle motor  304 . This would enable the power to the second spindle motor  354  and second actuator  360  to be reduced to a lower idle power (e.g., head parked, spindle revolutions per minute (RPM) reduced) for some part of the HDD  300  life cycle, thereby resulting in reduced power and operational cycles while still maintaining full performance to newer and likely more frequently accessed data. Then, once a sufficient amount of data is accumulated on the drive, data can begin to be stored on the other half of the drive such as on the second disk media  356  served by the second spindle motor  354 . When the HDD  300  usage capacity is lower, the drive will be able to use a lot less power to spin-up and operate, with power consumption increasing as capacity approaches the need to spin-up the second spindle motor  354  for example. Thus, according to an embodiment, spin-up of each spindle motor  304 ,  354  may be based on the current usage capacity of the drive, whereby HDD  300  may be controlled to spin-up only the spindle motor that controls the disk media where data will be written to or read from. Stated otherwise, HDD  300  is controlled to begin to spin-up one of the first and second spindle motors  304 ,  354  at a first time and begin to spin-up the other one of the first and second spindle motors  304 ,  354  at a second later time, possibly significantly into the future. When both spindle motors  304 ,  354  are needed, HDD  300  can also stagger the spin-up of the spindle motors  304 ,  354  to reduce the 12V (volt) spin-up peaks, thereby enabling HDD  300  to stay under specified power supply limits. 
     Additionally and according to an embodiment, a dual disk spindle motor such as HDD  300  may be utilized such that as particular data on the drive matures and requires fewer writes to it (e.g., temporally older data), that data can be moved to a certain portion of the first and second disk media  306 ,  356  ( FIGS.  3 - 4   ) while allocating the remainder of the disk media  306 ,  356  for more frequently accessed data. Indeed, it is contemplated that at some point in the use lifetime of HDD  300  it may be configured such that one of the first and second disk media  306 ,  356  stacks is used for mature data while the other is used for more newer, more operationally active data. Hence, the first or second spindle motor  304 ,  354  corresponding to the first or second disk media  306 ,  356  to which the mature data is moved may be set to the first rotational speed less than the second rotational speed to which the other of the first and second spindle motors  304 ,  354  is simultaneously set. 
     Typically, power and temperature issues are mitigated by balancing power and performance using various algorithms. In the context of a dual motor HDD such as HDD  300 , greater temperature control is also enabled. For example, based on S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology) attributes for temperature values or otherwise, responsive to HDD  300  identifying an increase in internal temperature that reaches a predetermined threshold value, HDD  300  can opt to reduce the RPM of one of the first or second spindle motors  304 ,  354 . This response to a temperature rise would thereby enable a non-trivial temperature reduction, such as to the motor base assembly, e.g., the first or second enclosure  308 ,  358  ( FIGS.  3 - 4   ). 
     Additionally, in a scenario in which a dual spindle motor design such as HDD  300  is implemented in combination with data storage devices configured with both SMR (shingled magnetic recording) and CMR (conventional magnetic recording), depending on the need of the customer, having a dual spindle motor design further enables more spindle motor control capabilities that could be taken advantage of to improve power, performance, and reliability of such products. In this context and according to an embodiment, the first actuator  310  and corresponding read-write transducers  110   a  of the first plurality of head sliders  110   b  are configured to read from and to write to the respective disk medium of the first disk media  306  utilizing one of a CMR technology and a SMR technology, while the second actuator  360  and corresponding read-write transducers  110   a  of the second plurality of head sliders  110   b  are configured to read from and to write to the respective disk medium of the second disk media  356  in the other of CMR and SMR technologies. 
     Thus, the foregoing control functions could be used to generally address the following issues, for non-limiting examples: (i) reduce the power consumption used when only half the disks are needed for reads/writes; (ii) reduce the power consumption used when a known number of disks are less frequently used; (iii) reduce the large 12V spin-up peak that results from pushing capacity by increasing the number of disks on a drive; and (iv) allow for greater temperature control. 
     Physical Description of Illustrative Operating Context(s) 
     Embodiments may be used in the context of a digital data storage device (DSD) such as a hard disk drive (HDD). Thus, in accordance with an embodiment, a plan view illustrating a conventional HDD  100  is shown in  FIG.  1    to aid in describing how a conventional HDD typically operates. 
       FIG.  1    illustrates the functional arrangement of components of the HDD  100  including a slider  110   b  that includes a magnetic read-write head  110   a . Collectively, slider  110   b  and head  110   a  may be referred to as a head slider. The HDD  100  includes at least one head gimbal assembly (HGA)  110  including the head slider, a lead suspension  110   c  attached to the head slider typically via a flexure, and a load beam  110   d  attached to the lead suspension  110   c . The HDD  100  also includes at least one recording medium  120  rotatably mounted on a spindle  124  and a drive motor (not visible) attached to the spindle  124  for rotating the medium  120 . The read-write head  110   a , which may also be referred to as a transducer, includes a write element and a read element for respectively writing and reading information stored on the medium  120  of the HDD  100 . The medium  120  or a plurality of disk media may be affixed to the spindle  124  with a disk clamp  128 . 
     The HDD  100  further includes an arm  132  attached to the HGA  110 , a carriage  134 , a voice-coil motor (VCM) that includes an armature  136  including a voice coil  140  attached to the carriage  134  and a stator  144  including a voice-coil magnet (not visible). The armature  136  of the VCM is attached to the carriage  134  and is configured to move the arm  132  and the HGA  110  to access portions of the medium  120 , all collectively mounted on a pivot shaft  148  with an interposed pivot bearing assembly  152 . In the case of an HDD having multiple disks, the carriage  134  may be referred to as an “E-block,” or comb, because the carriage is arranged to carry a ganged array of arms that gives it the appearance of a comb. 
     An assembly comprising a head gimbal assembly (e.g., HGA  110 ) including a flexure to which the head slider is coupled, an actuator arm (e.g., arm  132 ) and/or load beam to which the flexure is coupled, and an actuator (e.g., the VCM) to which the actuator arm is coupled, may be collectively referred to as a head-stack assembly (HSA). An HSA may, however, include more or fewer components than those described. For example, an HSA may refer to an assembly that further includes electrical interconnection components. Generally, an HSA is the assembly configured to move the head slider to access portions of the medium  120  for read and write operations. 
     With further reference to  FIG.  1   , electrical signals (e.g., current to the voice coil  140  of the VCM) comprising a write signal to and a read signal from the head  110   a , are transmitted by a flexible cable assembly (FCA)  156  (or “flex cable”, or “flexible printed circuit” (FPC)). Interconnection between the flex cable  156  and the head  110   a  may include an arm-electronics (AE) module  160 , which may have an on-board pre-amplifier for the read signal, as well as other read-channel and write-channel electronic components. The AE module  160  may be attached to the carriage  134  as shown. The flex cable  156  may be coupled to an electrical-connector block  164 , which provides electrical communication, in some configurations, through an electrical feed-through provided by an HDD housing  168 . The HDD housing  168  (or “enclosure base” or “baseplate” or simply “base”), in conjunction with an HDD cover, provides a semi-sealed (or hermetically sealed, in some configurations) protective enclosure for the information storage components of the HDD  100 . 
     Other electronic components, including a disk controller and servo electronics including a digital-signal processor (DSP), provide electrical signals to the drive motor, the voice coil  140  of the VCM and the head  110   a  of the HGA  110 . The electrical signal provided to the drive motor enables the drive motor to spin providing a torque to the spindle  124  which is in turn transmitted to the medium  120  that is affixed to the spindle  124 . As a result, the medium  120  spins in a direction  172 . The spinning medium  120  creates a cushion of air that acts as an air-bearing on which the air-bearing surface (ABS) of the slider  110   b  rides so that the slider  110   b  flies above the surface of the medium  120  without making contact with a thin magnetic-recording layer in which information is recorded. Similarly in an HDD in which a lighter-than-air gas is utilized, such as helium for a non-limiting example, the spinning medium  120  creates a cushion of gas that acts as a gas or fluid bearing on which the slider  110   b  rides. 
     The electrical signal provided to the voice coil  140  of the VCM enables the head  110   a  of the HGA  110  to access a track  176  on which information is recorded. Thus, the armature  136  of the VCM swings through an arc  180 , which enables the head  110   a  of the HGA  110  to access various tracks on the medium  120 . Information is stored on the medium  120  in a plurality of radially nested tracks arranged in sectors on the medium  120 , such as sector  184 . Correspondingly, each track is composed of a plurality of sectored track portions (or “track sector”) such as sectored track portion  188 . Each sectored track portion  188  may include recorded information, and a header containing error correction code information and a servo-burst-signal pattern, such as an ABCD-servo-burst-signal pattern, which is information that identifies the track  176 . In accessing the track  176 , the read element of the head  110   a  of the HGA  110  reads the servo-burst-signal pattern, which provides a position-error-signal (PES) to the servo electronics, which controls the electrical signal provided to the voice coil  140  of the VCM, thereby enabling the head  110   a  to follow the track  176 . Upon finding the track  176  and identifying a particular sectored track portion  188 , the head  110   a  either reads information from the track  176  or writes information to the track  176  depending on instructions received by the disk controller from an external agent, for example, a microprocessor of a computer system. 
     An HDD&#39;s electronic architecture comprises numerous electronic components for performing their respective functions for operation of an HDD, such as a hard disk controller (“HDC”), an interface controller, an arm electronics module, a data channel, a motor driver, a servo processor, buffer memory, etc. Two or more of such components may be combined on a single integrated circuit board referred to as a “system on a chip” (“SOC”). Several, if not all, of such electronic components are typically arranged on a printed circuit board that is coupled to the bottom side of an HDD, such as to HDD housing  168 . 
     References herein to a hard disk drive, such as HDD  100  illustrated and described in reference to  FIG.  1   , may encompass an information storage device that is at times referred to as a “hybrid drive”. A hybrid drive refers generally to a storage device having functionality of both a traditional HDD (see, e.g., HDD  100 ) combined with solid-state storage device (SSD) using non-volatile memory, such as flash or other solid-state (e.g., integrated circuits) memory, which is electrically erasable and programmable. As operation, management and control of the different types of storage media typically differ, the solid-state portion of a hybrid drive may include its own corresponding controller functionality, which may be integrated into a single controller along with the HDD functionality. A hybrid drive may be architected and configured to operate and to utilize the solid-state portion in a number of ways, such as, for non-limiting examples, by using the solid-state memory as cache memory, for storing frequently-accessed data, for storing I/O intensive data, and the like. Further, a hybrid drive may be architected and configured essentially as two storage devices in a single enclosure, i.e., a traditional HDD and an SSD, with either one or multiple interfaces for host connection. 
     Expensions and Alternatives 
     In the foregoing description, embodiments of the invention have been described with reference to numerous specific details that may vary from implementation to implementation. Therefore, various modifications and changes may be made thereto without departing from the broader spirit and scope of the embodiments. Thus, the sole and exclusive indicator of what is the invention, and is intended by the applicants to be the invention, is the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. Any definitions expressly set forth herein for terms contained in such claims shall govern the meaning of such terms as used in the claims. Hence, no limitation, element, property, feature, advantage or attribute that is not expressly recited in a claim should limit the scope of such claim in any way. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. 
     In addition, in this description certain process steps may be set forth in a particular order, and alphabetic and alphanumeric labels may be used to identify certain steps. Unless specifically stated in the description, embodiments are not necessarily limited to any particular order of carrying out such steps. In particular, the labels are used merely for convenient identification of steps, and are not intended to specify or require a particular order of carrying out such steps.