Patent ID: 12249350

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.

DETAILED DESCRIPTION

In the following, reference is made to embodiments of the disclosure. However, it should be understood that the disclosure is not limited to specific described embodiments. Instead, any combination of the following features and elements, whether related to different embodiments or not, is contemplated to implement and practice the disclosure. Furthermore, although embodiments of the disclosure may achieve advantages over other possible solutions and/or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the disclosure. Thus, the following aspects, features, embodiments and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to “the disclosure” shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s).

The present disclosure generally relates to a tape drive comprising a tape wound around first and second tape reels and a tape head module configured to write data to and read data from the tape. The tape drive is configured to equalize the amount of time the tape spends stored in a first state and a second state when being stored long term, or when in a preservation phase, to minimize the effects of creep and tape dimensional stability. In the first state, a majority of the tape is wound around the first tape reel. In the second state, the majority of the tape is wound around the second tape reel. The tape drive is configured to move the tape between the first and second states: (1) upon being triggered by the timer, or (2) based on the tape head module being utilized to determine a position error signal.

FIGS.1A-1Cillustrate a perspective exploded view, a simplified top down, and side profile view of a tape drive100, in accordance with some embodiments. The tape drive100may be a tape embedded drive (TED). Focusing onFIG.1B, for example, the tape drive comprises a casing105, one or more tape reels110, one or more motors (e.g., a stepping motor120(also known as a stepper motor), a voice coil motor (VCM)125, etc.) a head assembly130with one or more read heads and one or more write heads, and tape guides/rollers135a,135b. In the descriptions herein, the term “head assembly” may be referred to as “magnetic recording head”, interchangeably, for exemplary purposes. Focusing onFIG.1C, for example, the tape drive further comprises a printed circuit board assembly (PCBA)155. In an embodiment, most of the components are within an interior cavity of the casing, except the PCBA155, which is mounted on an external surface of the casing105. The same components are illustrated in a perspective view inFIG.1A. In the descriptions herein, the term “tape” may be referred to as “magnetic media”, interchangeably, for exemplary purposes.

In the illustrated embodiments, two tape reels110are placed in the interior cavity of the casing105, with the center of the two tape reels110on the same level in the cavity and with the head assembly130located in the middle and below the two tape reels110. Tape reel motors located in the spindles of the tape reels110can operate to wind and unwind the tape media115in the tape reels110. Each tape reel110may also incorporate a tape folder to help the tape media115be neatly wound onto the reel110. One or more of the tape reels110may form a part of a removable cartridge and are not necessarily part of the tape drive100. In such embodiments, the tape drive100may not be a tape embedded drive as it does not have embedded media, the drive100may instead be a tape drive configured to accept and access magnetic media or tape media115from an insertable cassette or cartridge (e.g., an LTO drive), where the insertable cassette or cartridge further comprises one or more of the tape reels110as well. In such embodiments, the tape or media115is contained in a cartridge that is removable from the drive100. The tape media115may be made via a sputtering process to provide improved areal density. The tape media115comprises two surfaces, an oxide side and a substrate side. The oxide side is the surface that can be magnetically manipulated (written to or read from) by one or more read/write heads. The substrate side of the tape media115aids in the strength and flexibility of the tape media115.

Tape media115from the tape reels110are biased against the guides/rollers135a,135b(collectively referred to as guides/rollers135) and are movably passed along the head assembly130by movement of the reels110. The illustrated embodiment shows four guides/rollers135a,135b, with the two guides/rollers135afurthest away from the head assembly130serving to change direction of the tape media115and the two guides/rollers135bclosest to the head assembly130by pressing the tape media115against the head assembly130.

As shown inFIG.1A, in some embodiments, the guides/rollers135utilize the same structure. In other embodiments, as shown inFIG.1B, the guides/rollers135may have more specialized shapes and differ from each other based on function. Furthermore, a lesser or a greater number of rollers may be used. For example, the two function rollers may be cylindrical in shape, while the two functional guides may be flat-sided (e.g., rectangular prism) or clip shaped with two prongs and the film moving between the prongs of the clip.

The voice coil motor125and stepping motor120may variably position the tape head(s) transversely with respect to the width of the recording tape. The stepping motor120may provide coarse movement, while the voice coil motor125may provide finer actuation of the head(s). In an embodiment, servo data may be written to the tape media to aid in more accurate position of the head(s) along the tape media115.

In addition, the casing105comprises one or more particle filters141and/or desiccants142, as illustrated inFIG.1A, to help maintain the environment in the casing. For example, if the casing is not airtight, the particle filters may be placed where airflow is expected. The particle filters and/or desiccants may be placed in one or more of the corners or any other convenient place away from the moving internal components. For example, the moving reels may generate internal airflow as the tape media winds/unwinds, and the particle filters may be placed within that airflow.

There is a wide variety of possible placements of the internal components of the tape drive100within the casing105. In particular, as the head mechanism is internal to the casing in certain embodiments, the tape media115may not be exposed to the outside of the casing105, such as in conventional tape drives. Thus, the tape media115does not need to be routed along the edge of the casing105and can be freely routed in more compact and/or otherwise more efficient ways within the casing105. Similarly, the head(s)130and tape reels110may be placed in a variety of locations to achieve a more efficient layout, as there are no design requirements to provide external access to these components.

As illustrated inFIG.1C, the casing105comprises a cover150and a base145. The PCBA155is attached to the bottom, on an external surface of the casing105, opposite the cover150. As the PCBA155is made of solid state electronics, environmental issues are less of a concern, so it does not need to be placed inside the casing105. That leaves room inside casing105for other components, particularly, the moving components and the tape media115that would benefit from a more protected environment.

In some embodiments, the tape drive100is sealed. Sealing can mean the drive is hermetically sealed or simply enclosed without necessarily being airtight. Sealing the drive may be beneficial for tape film winding stability, tape film reliability, and tape head reliability. Desiccant may be used to limit humidity inside the casing105.

In one embodiment, the cover150is used to hermetically seal the tape drive. For example, the drive100may be hermetically sealed for environmental control by attaching (e.g., laser welding, adhesive, etc.) the cover150to the base145. The drive100may be filled by helium, nitrogen, hydrogen, or any other typically inert gas.

In some embodiments, other components may be added to the tape drive100. For example, a pre-amp for the heads may be added to the tape drive. The pre-amp may be located on the PCBA155, in the head assembly130, or in another location. In general, placing the pre-amp closer to the heads may have a greater effect on the read and write signals in terms of signal-to-noise ratio (SNR). In other embodiments, some of the components may be removed. For example, the filters141and/or the desiccant142may be left out.

In various embodiments, the drive100includes controller140integrated circuits (IC) (or more simply “a controller140”) (e.g., in the form of one or more System on Chip (SoC)), along with other digital and/or analog control circuitry to control the operations of the drive. For example, the controller140and other associated control circuitry may control the writing and reading of data to and from the magnetic media, including processing of read/write data signals and any servo-mechanical control of the media and head module. In the description below, various examples related to writing and reading and verifying of written data, as well as control of the tape head and media to achieve the same, may be controlled by the controller140. As an example, the controller140may be configured to execute firmware instructions for the various same gap verify embodiments described below.

FIG.2is a schematic illustration of a tape head module assembly200and a tape204that are aligned. The tape head module assembly200comprises a tape head body202that is aligned with the tape204. The tape204moves past the tape head module assembly200during read and/or write operations. The tape head module assembly200has a media facing surface (MFS)214that faces the tape204. The tape head module assembly200is coupled to a controller, which may be the controller140ofFIG.1.

The tape head body202comprises a first servo head206A and a second servo head206B spaced therefrom. It is to be understood that while two servo heads have been shown, the disclosure is not limited to two servo heads. Rather, it is contemplated that more or less servo heads may be present. A plurality of data heads208A-208G is disposed between the first servo head206A and the second servo head206B. It is to be understood that while seven data heads have been shown, the disclosure is not limited to seven data heads. Rather, the number of data heads can be more or less than seven, depending on the requirements of the embodiment. For example there can be sixteen, thirty two, sixty four or more data heads utilized in the tape head body202.

A plurality of pads220A-220N is electrically coupled to the data head body202. The plurality of pads220A-220N coupled to the data head body202is not limited to the number shown inFIG.2. Rather, more or less pads are contemplated. The pads220A-220N are used to connect the drive electronics to the servo heads206A,206B and to data read and writer elements. The pads220A-220N are used to establish the potential across the servo reader by means of a power supply (not shown) embedded in the tape head200.

The tape204comprises a first servo track210A and a second servo track210B. The first servo track210A and the second servo track210B are spaced apart allowing the tape head200to monitor and control the average position of the data heads208A-208G relative to the data tracks212A-212G on the tape204. It is to be understood that while two servo tracks have been shown, the disclosure is not limited to two servo tracks. Rather, the number of servo tracks can be more or less than two, depending on the requirements of the embodiment.

The tape204further comprises a plurality of data tracks212A-212G disposed between the first servo track210A and the second servo track210B. It is to be understood that while seven data tracks have been shown, the disclosure is not limited to the seven data tracks. Rather, the number of data tracks can be more or less than seven, depending on the requirements of the embodiment. In the embodiment ofFIG.2, the first servo head206A reads its lateral position information (e.g., alignment) over the first servo track210A. The second servo head206B is aligned with the second servo track210B. The combined information allows the servo actuator of the tape drive200to align the data heads208A-208G such that the center data head (e.g.,208D) is centered on tape204. The plurality of data heads208A-208G is thus individually aligned with the plurality of data tracks212A-212N for best case positioning. In this embodiment the first servo head206A, the second servo head206B, the first servo track210A, the second servo track210B, the plurality of data heads208A-208G, and the plurality of data tracks212A-212G are able to read and/or write the data accurately because all are aligned perpendicular to the direction of travel of the tape204.

FIGS.3A-5Billustrate conventional conditions or methods of storing a tape of a tape drive.FIG.3Aillustrates a first condition300of storing a tape302, andFIG.3Billustrates the deformations of storing the tape302using the first condition300, represented by line320.FIG.4Aillustrates a second condition400of storing a tape402, andFIG.4Billustrates the deformations of storing the tape402using the second condition400, represented by line420.FIG.5Aillustrates a third condition500of storing a tape502, andFIG.5Billustrates the deformations of storing the tape502using the third condition500, represented by line520. InFIGS.3B,4B, and5B, the line321represents a width of a tape that has not experienced the effects of creep or TDS.

In the first condition300of storing a tape302shown inFIG.3A, a first tape reel304has no or few turns of tape302wound around it, and a second tape reel306has all or most of the tape302wound around it. If the tape302is stored as shown inFIG.3Afor a long period of time, a width of the tape302becomes narrower (−) near beginning of the tape (BOT) and wider (+) near an end of the tape (EOT), like shown inFIG.3B. As such, the track width of the tape302various along the width of the tape302.

In the second condition400of storing a tape402shown inFIG.4A, a first tape reel404has all or most of the tape402wound around it, and a second tape reel406has no or few turns of tape402wound around it, or the opposite of the first condition300. If the tape402is stored as shown inFIG.4Afor a long period of time, a width of the tape402becomes wider near the BOT and narrower near the EOT, like shown inFIG.4B. As such, the track width of the tape402various along the width of the tape402.

In the third condition500of storing a tape502shown inFIG.5A, a first tape reel504and a second tape reel506each have about the same length of tape502wound around them. If the tape502is stored as shown inFIG.5Afor a long period of time, a width of the tape502becomes narrower around the midpoint or midsection of the tape502(i.e., a central portion of the tape502disposed between the BOT and the EOT) and the tape502becomes wider at both the BOT and the EOT due to the effects of creep, like shown inFIG.5B. As such, the track width of the tape502various along the width of the tape502.

FIGS.6A-6Dillustrate the tape302ofFIGS.3A-3Bbeing read by a tape head610of a tape drive after being stored like discussed in the first condition300. As discussed above, a beginning portion302aof the tape302extending from the BOT to line601has a narrower width or track pitch, a central portion302bof the tape302extending from line601to line603has not been stretched or compressed, and an end portion302cof the tape302extending from line603to the EOT has a wider width or track pitch.

InFIG.6A, the line620represents the width of the tape302after being stored, and the box622shows the area of the tape302where data is readable (e.g., a readable zone), or where a pitch of the data elements612is substantially equal to a pitch of the tracks318of the tape302.

FIG.6Bshows the tape head610comprising a plurality of data elements612, where each data element612comprises a write transducer and a read transducer, disposed over the beginning portion302aof the tape302. Each data element612of the tape head610should align with a track318of the tape302. However, as shown by the circle614, a number of data elements612are unaligned with their respective track318, as the pitch of the data elements612is greater than the pitch of the tracks318due to the effects of creep and/or TDS causing the beginning portion302ato be narrower. As such, the data written to the beginning portion302ais not within the readable zone indicated by the box622ofFIG.6A, resulting in a read error.

FIG.6Cshows the tape head610disposed over the central portion302bof the tape302. Since the central portion302bdid not experience the effects of creep and/or TDS as severely as the beginning portion302aor the end portion302c, the pitch of the data elements612is substantially equal to a pitch of the tracks318of the tape302. As such, each data element312is substantially aligned with its respective track318, and the data written to the central portion302bis within the readable zone indicated by the box622ofFIG.6A.

FIG.6Dshows the tape head610disposed over the end portion302cof the tape302. As shown by the circle616, a number of data elements612are unaligned with their respective track318, as the pitch of the data elements612is less than the pitch of the tracks318due to the effects of creep and/or TDS causing the beginning portion302ato be wider. As such, the data written to the end portion302cis not within the readable zone indicated by the box622ofFIG.6A, resulting in a read error.

FIGS.7A-7Billustrate a tape drive700in two different states, state A and state B, according to various embodiments.FIG.8Aillustrates a method800of storing a tape702of the tape drive700, according to one embodiment.FIG.8Billustrates the tape702after being stored for a long period of time using the method800ofFIG.8A, according to one embodiment. The tape drive700may be the tape drive100ofFIGS.1A-1C. The tape drive700may comprise the tape head module assembly200ofFIG.2.

The tape drive700comprises a first tape reel704and a second tape reel706, around which the tape702is wound. The tape702is biased against one or more guides/rollers735and is movably passed along a head assembly or tape head710by movement of the reels704,706using a reel motor732. The reel motor732is coupled to each tape reel704,706, and is configured to rotate the tape reels704,706. The tape head710comprises a plurality of data elements712(shown inFIGS.9A-9C), where each data element712comprises a write transducer and a read transducer. The tape head710may be the tape head module assembly200ofFIG.2. Thus, the tape head710may be referred to herein as a tape head module.

The tape drive700further comprises a controller730, a memory unit734, such as a non-volatile memory unit or a tape cartridge, and a timer736. The memory unit734may be within the controller730, or the memory unit734may be separate from the controller730. The timer736may be coupled to the memory unit734. In some embodiments, the timer736is optional if a host device (not shown) comprises a timer. The timer736may be within the controller730, or the timer736may be separate from the controller730.

FIG.7Aillustrates the tape drive700storing the tape702in state A, or a first state. In state A, the first tape reel704has no or few turns of tape702wound around it, and the second tape reel706has all or most of the tape702wound around it.FIG.7Billustrates the tape drive700storing the tape702in state B, or a second state. In state B, the first tape reel704has all or most of the tape702wound around it, and the second tape reel706has no or few turns of tape702wound around it. Utilizing the method800ofFIG.8, the tape702spends substantially the same amount of time in both state A and in state B, as discussed below.

FIG.8Aillustrates a method800of storing the tape702of the tape drive700, according to one embodiment. It is assumed in the method800that the tape702starts off being stored in state A shown inFIG.7A; however, the tape702may instead start off being stored in state B shown inFIG.7B.

In operation810, the amount of time the tape702spends stored in state A is determined, such as by recording the amount of time. While recording is used herein as a method of determining the amount of time spent in a particular state, recording is merely an example, and other methods may be used as well. The amount of time is stored in the memory unit734, and may be recorded using the timer736or the controller730. Upon the timer736being triggered a first time after a predetermined amount of time has passed, such as several days to several months, the controller730is configured to read the amount of time recorded in operation820. The predetermined amount of time may vary depending on the validation of each tape drive system.

In operation830, the tape702is moved to state B. The amount of time the tape702spends stored in state B is determined, such as by recording the amount of time, in operation840. The amount of time is stored in the memory unit734, and may be recorded using the timer736or the controller730. Upon the timer736being triggered a second time after the predetermined amount of time has passed, the controller730is configured to read the amount of time recorded in operation850. The predetermined amount of time to trigger the timer736may be the same in both operations820and850.

In operation860, a different between the amount of time the tape702spent stored in state A and state B is determined, such as by the controller730. If the difference between the amounts of time the tape702spent stored in state A and state B indicates that the tape702spent more time in state B than in state A, the method800proceeds to operation870. In operation870, the tape702is moved back to state A, and the method800starts over and proceeds from operation810. If the difference between the amounts of time the tape702spent stored in state A and state B indicates that the tape702spent more time in state A than in state B, the method800proceeds to operation875, rather than to operation870. In operation875, the tape702remains in state B, and the method800then proceeds to continue from to operation840. If the difference between the amounts of time the tape702spent stored in state A and state B is determined to be substantially the same, the method800may proceed to either operation870or to operation875in order to make the amount of time spent in state A equal to the amount of time spent in state B.

By recording the amount of time the tape702spends in both state A and in state B, the tape702can be adjusted to equalize the amounts of time spent in state A and state B to reduce the effects of creep and TDS.FIG.8Billustrates the tape702after having been stored using the method800. As shown inFIG.8B, the entire length of the tape702, from the BOT to the EOT, has very little or no width variations. Thus, there are no portions of the tape702that are outside of a readable zone.

FIGS.9A-9Cillustrate the tape drive700ofFIGS.7A-7Breading a tape902after the tape902has been stored in various different states, according to another embodiment.FIG.9Aillustrates a portion of the tape902being stored in state A, shown inFIG.7A,FIG.9Billustrates a portion of the tape902being stored in a manner resulting in the tape902having little to no width variations, like shown inFIG.8B, andFIG.9Cillustrates a portion of the tape902being stored in state B, shown inFIG.7B.FIGS.9A-9Cmay represent different portions across a length of the same tape902.

In addition to comprising the plurality of data elements712, the tape head710further comprises a first servo head740aand a second servo head740b. The plurality of data elements712are disposed between the first servo head740aand the second servo head740b. The tape902comprises a first servo pattern942aand a second servo pattern942b, where the plurality of data tracks918of the tape902are disposed between the first servo pattern942aand the second servo pattern942b. The first servo head740ais configured to read the first servo pattern942aand the second servo head740bis configured to read the second servo pattern942b. Each servo pattern942a,942bcomprises a plurality of lines arranged in a chevron pattern. The servo heads740a,740bread the servo patterns942a,942bin order to determine the positioning of the tape head710, as well as to determine a state of the tape902, such as whether the tape902has being wider or narrower in portions. The servo heads740a,740bmay be referred to herein as servo elements or servo readers.

FIG.10illustrates a method1000of storing the tape902of the tape drive700using the first and second servo heads740a,740b, according to another embodiment.

In operation1010, the tape head710obtains a first position signal of a first servo head740aand a second position signal of a second servo head740bsimultaneously at various locations across the entire length of the tape902. For example, inFIG.9A, the first servo head740ahas a first position signal944awhen reading the first servo pattern942a; inFIG.9B, the first servo head740ahas a first position signal946awhen reading the first servo pattern942a; and inFIG.9C, the first servo head740ahas a first position signal948awhen reading the first servo pattern942a. The first position signals944a,946a, and948aare all substantially aligned with the center of the first servo pattern942a.

InFIG.9A, the second servo head740bhas a second position signal944bwhen reading the second servo pattern942b; inFIG.9B, the second servo head740bhas a second position signal946bwhen reading the second servo pattern942b; and inFIG.9C, the second servo head740bhas a second position signal948bwhen reading the second servo pattern942b. InFIG.9A, the second position signal944bis towards a bottom of the second servo pattern942b(i.e., further from the data tracks918). InFIG.9B, the second position signal946bis substantially aligned with the center of the second servo pattern942b, and thus, at a same location as the first position signal946a. InFIG.9C, the second position signal948bis towards a top of the second servo pattern942b(i.e., closer to the data tracks918).

In operation1020, an average difference between the first position signal and the second position signal across the length of the tape902is calculated to determine a delta position error signal (PES). The delta PES is a measurement of the degree of the tape902width expansion and contraction. By determining the delta PES over the entire tape length, it is possible to determine whether the average tape width variation is close to state A (shown inFIG.7A) or to state B (shown inFIG.7B).

In operation1030, the tape902is moved to either state A or state B based on the average difference. InFIG.9A, the average difference between the first position signal944aand the second position signal944bindicates that the overall width of the tape902has narrowed due to creep. In other words, the average difference indicates that the first position signal944ais spaced too far from the second position signal944b. Thus, the tape902would be moved to state B to counter the effects of being in state A for too long.

InFIG.9B, the average difference between the first position signal946aand the second position signal946bindicates that the overall width of the tape902has not altered much, if any. In other words, the average difference indicates that the first servo position946aaligns with the second position signal946b. As such, the tape902may remain in whatever state it is currently in.

InFIG.9C, the average difference between the first position signal948aand the second position signal948bindicates that the overall width of the tape902has widened due to creep. In other words, the average difference indicates that the first position signal948ais spaced too close to the second position signal948b. Thus, the tape902would be moved to state A to counter the effects of being in state B for too long.

Upon completion of operation1030, the method1000repeats one or more times, or as needed. In some embodiments, the method1000is triggered by a timer736after a predetermined time.

FIG.11illustrates a graph1100of a life cycle of a tape drive, such as the tape drive700ofFIGS.7A-7B, according to one embodiment. In the graph1100, the y-axis represents the amount of data stored to the tape drive, and the x-axis represents time.

In a first phase1110, or the create phase1110, of the graph1100, new information is written to the tape, such as the tape702or the tape902. When data is created and written to the tape, the value of the data is at its highest, meaning that there are few to no errors when reading the data or writing the data to the tape. After the data is written in the first phase1110, the data is used in the second phase1120, or the use phase1120. Using the data may involve writing new data, analyzing the data, and/or processing the data.

In the third phase1130, or the reference phase1130, the data written in phases1110and1120is referred to a plurality of times. Referring to the data may include retrieving and reading any written data. When the tape drive700is in the refer phase1130, the tape is in a state C, which emphasizes access performance for retrieval of data. In state C, the tape is alternatingly and repeatedly moved between state A and state B as needed to locate where particular data is stored. As such, there is very little creep or TDS effects on the tape, as the tape is not left in a particular state for a prolonged period of time.

In the fourth phase1140, or the preserve phase1140, the tape drive700goes into a preservation mode, where the tape, and the data stored on the tape, are securely stored for a long period of time. In the preserve phase1140, access to stored data is very rare. As noted by the graph1100, the tape drive700is in the preserve phase1140is a substantially greater amount of time than it is in any of the create, use, and/or reference phases1110,1120,1130. The value of the data or information stored on the tape decreases rapidly from the create phase1110throughout the preserve phase1140. Conversely, the amount of data stored on the tape increases from the create phase1110throughout the preserve phase1140. In the fifth phase1150, or the delete phase1150, the data stored on the tape is securely erased.

In general, the tape drive700spends the majority of the time in the reference phase1130and in the preserve phase1140. The tape drive700may determine what phase the tape and/or data is in by measuring how often data is accessed. If the frequency of accessing data decreases below a certain threshold or level, the tape drive700can then determine that the tape has entered the preservation phase1140. Upon determining that the tape is in the preservation phase1140, the tape drive700may then implement either method800ofFIG.8Aor method1000ofFIG.10to reduce the effects of creep and TDS.

Alternatively, a host drive (not shown) coupled to the tape drive700may determine what phase the tape drive700and/or tape are in. The host drive may prepare a command that distinguishes between the reference phase1130and the preservation phase1140. When the host device recognizes that the reference phase1130has ended, the host device may then send a command to the tape drive to move to the preservation phase1140. Upon entering the preservation phase1140, the tape drive700may then implement either method800ofFIG.8Aor method1000ofFIG.10to reduce the effects of creep and TDS. Thus, both method800and method1000may be individually implemented upon determining which phase the tape is in, or upon receiving a command to enter a particular phase.

Therefore, by ensuring a tape spends an equal amount of time in both state A and state B, the effects of creep and TDS can be minimized. Minimizing the effects of creep and TDS result in the tape having a greater lifetime, and protects the reliability and integrity of the data stored on the tape. As such, controlling the amount of tape wound around each tape reel enables the tape to have a narrower track width, thus increasing the storage capacity of the tape drive.

In one embodiment, a tape drive comprises a first tape reel, a second tape reel, and a tape head disposed between the first tape reel and the second tape reel, wherein a tape is configured to be wound around the first tape reel and the second tape reel, wherein, when storing the tape, the tape drive is configured to: (A) determine a first amount of time the tape spends in a first state, wherein, in the first state, a majority of the tape is wound around the first tape reel, (B) move the tape to a second state, wherein, in the second state, the majority of the tape is wound around the second tape reel, (C) determine a second amount of time the tape spends in the second state, (D) determine a difference between the first amount of time and the second amount of time, and (E) based on the difference, move the tape to the first state or remain in the second state.

The tape drive is configured to repeat preforming (A)-(E) one or more times, and wherein (A)-(E) are performed when in a preservation phase where data stored on the tape is rarely or never accessed. The tape drive further comprises a memory device, wherein the first amount of time and the second amount of time are recorded to the memory device. The tape drive further comprises a timer, wherein the tape drive is further configured to: upon a first trigger of the timer, read the recorded first amount of time prior to moving the tape to the second state, and upon a second trigger of the time, read the recorded second amount of time prior to determining the difference. If the difference determined shows the tape spent more time in the second state than in the first state, the tape drive is configured to move the tape to the first state, and if the difference determined shows the tape spent more time in the first state than in the second state, the tape drive is configured to remain in the second state. If the difference determined shows the first amount of time is substantially equal to the second amount of time, the tape is moved to the first state, or the tape remains in the second state.

In another embodiment, a tape drive comprises a first tape reel, a second tape reel, a tape comprising a first servo pattern, a second servo pattern, and a plurality of data tracks disposed between the first servo pattern and the second servo pattern, wherein the tape is wound around the first tape reel and the second tape reel, and a tape head disposed between the first tape reel and the second tape reel, the tape head comprising: a first servo element, a second servo element, and a plurality of data elements disposed between the first servo element and the second servo element, wherein the tape drive is configured to: (A) obtain a first position signal of the first servo element and a second position signal of the second servo element simultaneously at a plurality of locations across an entire length of the tape, (B) calculate an average difference between the first position signal and the second position signal, and (C) based on the average difference, move the tape to a first state, wherein a majority of the tape is wound around the first tape reel in the first state, move the tape to a second state, wherein the majority of the tape is wound around the second tape reel in the second state, or remain in a current state, the current state being the first state or the second state.

The average difference indicates that the first position signal is spaced a distance over a first threshold away from the second position signal, the tape is moved to the second state. The average difference indicates that the first position signal is spaced a distance over a second threshold near to the second position signal, the tape is moved to the first state. The average difference indicates that the first position signal is substantially aligned with the second position signal, the tape remains in the current state. The tape drive is configured to determine a phase of the tape prior to obtaining the first position signal and the second position signal. The tape drive is configured to receive a command to enter a preservation phase prior to obtaining the first position signal and the second position signal. The tape drive further comprises a timer, wherein the tape drive is configured to obtain the first position signal and the second position signal upon the timer being triggered one or more times. The tape drive is configured to repeat preforming (A)-(C) one or more times, and wherein (A)-(C) are performed when in a preservation phase where data stored on the tape is rarely or never accessed.

In yet another embodiment, a tape drive comprises a timer, a first tape reel, a second tape reel, a tape head disposed between the first tape reel and the second tape reel, a tape wound around the first tape reel and the second tape reel, means for recording a first amount of time the tape spends in a first state, wherein a majority of the tape is wound around the first tape reel in the first state, means for reading the recorded first amount of time upon a first trigger of the timer, means for moving the tape to a second state, wherein the majority of the tape is wound around the second tape reel in the second state, means for recording a second amount of time the tape spends in the second state, means for reading the recorded second amount of time, and means for determining a difference between the first amount of time and the second amount of time, wherein the tape drive is configured to move the tape to the first state or remain in the second state based on the difference.

The preservation phase is a phase of the tape when data of the tape is rarely or never accessed. The tape drive further comprises means for determining when the tape is in the preservation phase. The tape drive is configured to receive a command to enter the preservation phase. The tape drive further comprises a non-volatile memory device, wherein the first amount of time and the second amount of time are recorded to the non-volatile memory device. If the difference determined shows the tape spent more time in the second state than in the first state, the tape drive is configured to move the tape to the first state, and if the difference determined shows the tape spent more time in the first state than in the second state, the tape drive is configured to remain in the second state.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.