Patent Publication Number: US-2002012579-A1

Title: Data storage system with redundant media handling assemblies

Description:
[0001] This application is a continuation of U.S. application, Ser. No. 09/311, 243 filed on May 13, 1999, which is hereby incorporated by reference for all that is disclosed therein.  
     FIELD OF THE INVENTION  
     [0002] The present invention relates generally to data storage systems for handling and storing data storage media devices such as data cartridges, and more particularly to a data storage system having redundant media handling assemblies. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0003] Data storage in the computer industry is accomplished in a number of ways. For example, data may be stored on various data storage media devices such as tapes, compact disks, “floppy” or “hard ” disks, and the like. Oftentimes, data storage media which is transferrable from one location to another is housed within a parallelepiped-shaped cartridge. It is to be understood that the term “cartridge ” or “data cartridge ” as used in the present application encompasses any data storage media device, whether or not it is housed within a cartridge.  
       [0004] Data storage systems are used to store data cartridges at known locations and to retrieve desired cartridges so that data may be written to or read from the cartridges. A typical data storage system may include different types of cartridge receiving devices. For example, one type of cartridge receiving device is a cartridge storage rack or“magazine ” which has a plurality of individual cartridge storage locations. Another type of cartridge receiving device is a cartridge read/write device or “drive ”. A data storage system may also include a cartridge handling assembly for retrieving data cartridges and translating them among cartridge receiving devices (e.g., from a cartridge storage location to a drive and vice-versa).  
       [0005] Data storage systems may be produced in a variety of sizes and configurations. One type of data storage system has a guide track extending along the length of a central vertical shaft. A single data cartridge handling assembly or“picker ” assembly is vertically displaceable along the track and is adapted to move data cartridges between cartridge receiving devices positioned adjacent to the central vertical shaft in vertically stacked layers or tiers. In some storage systems of this type all components are provided in a single housing unit. In other storage systems of this type a plurality of modular housing units are stacked one on top of the other to provide a compound housing assembly. In a compound housing assembly each modular housing unit contains a portion of the vertical shaft and one or more of the tiers of cartridge receiving devices of the data storage system. Such an assembly of modular units is disclosed in U.S. Patent Application Ser. No. 09/137,350 filed Aug. 20, 1998 for MODULAR DATA STORAGE SYSTEM of Joseph M. White, Matthias Lester, and Dave Jones, which is hereby incorporated for all that it discloses. An advantage of an integral data storage system having multiple vertically stacked tiers accessible by a single picker assembly over systems having multiple independent single tier units, each with its own picker assembly, is that it obviates the need to coordinate the operation of multiple systems. Also, unnecessary duplication of certain system components, such as drives and pickers, is avoided. However one disadvantage of a unitary system having a single picker assembly is that a failure of the picker assembly causes loss of access to all of the media in the storage system until the picker is repaired or replaced. It would be generally desirable to provide a data storage system having multiple vertically stacked tiers accessible by a single picker assembly with a subsystem which would automatically replace a nonoperating picker assembly with an operating picker assembly so that the user&#39;s access to data stored in the system is not interrupted.  
       SUMMARY OF THE INVENTION  
       [0006] The present invention is directed to a data storage system for handling and storing data storage media. The system ordinarily uses a single main media picker assembly to move media between media receiving devices positioned along a picker displacement path. If the main picker assembly fails it is automatically removed from a portion of the path associated with media access and is replaced by a “fall back”/“back up”/“redundant ” picker assembly which continues operation of the data storage system without significant interruption.  
       [0007] Thus the invention may comprise a data storage system comprising: a housing assembly having a first end and a second end and having an open shaft extending between said first end and said second end and comprising: a first housing unit having a first portion of said open shaft extending therethrough, said first unit being positioned proximate said first end of said housing assembly; a second housing unit having a second portion of said open shaft extending therethrough, said second unit being positioned proximate said second end of said housing assembly; at least a third housing unit having a third portion of said open shaft extending therethrough having a plurality of data media receiving devices mounted therein, said third housing unit being disposed between said first and second housing units; a first media handling assembly displaceably positioned within said open shaft; and a second media handling assembly displaceably positioned within said open shaft.  
       [0008] The invention may also comprise a data storage system comprising: a media picker displacement path having a first end and a second end; a first media picker assembly mounted in the picker displacement path; a second media picker assembly mounted in the picker displacement path; a plurality of data storage media access locations located along the picker displacement path; the first media picker assembly being displaceable along the path from the first end to a point of interfering contact with the second media picker assembly; the second media picker assembly being displaceable along the path from the second end to a point of interfering contact with the first media picker assembly.  
       [0009] The invention may also comprise a method of operating a data storage library comprising: moving data storage media between media holding positions located along a one-picker-at-a-time picker displacement path with a first media picker assembly until the first media picker assembly malfunctions; after it malfunctions moving the first picker assembly to a first end of the picker displacement path; maintaining a second media picker assembly at a stationary position at a second end portion of the picker displacement path until the first picker assembly malfunctions; after the first picker assembly malfunctions moving data storage media between media holding positions located along the picker displacement path with the second picker assembly. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] Illustrative and presently preferred embodiments of the invention are shown in the accompanying drawings in which:  
     [0011]FIG. 1 is an isometric view of a modular data storage system;  
     [0012]FIG. 2 is an isometric view of a modular unit from the modular data storage system of FIG. 1, with most of the housing broken away;  
     [0013]FIG. 3 is a top plan view of the modular unit of FIG. 2 schematically illustrating a preferred mounting position of the actuator system and pinion gear assembly;  
     [0014]FIG. 4 schematically illustrates an alternative longitudinal mounting position for the actuator system and pinion gear assembly of FIG. 3;  
     [0015]FIG. 5 schematically illustrates an alternative lateral mounting position for the actuator system and pinion gear assembly of FIG. 3;  
     [0016]FIG. 6 is an enlarged side elevational view schematically illustrating an upper rack and a lower rack from two adjacent modular units and a pinion gear of the modular data storage system of FIG. 1; and  
     [0017]FIG. 7 is an isometric view of modular units from the modular data storage system of FIG. 1 mounted within a rack mount type housing.  
     [0018]FIG. 8 is a schematic cross sectional elevation view of a data storage system in a shipping/pre-startup mode.  
     [0019]FIG. 9 is a schematic cross sectional elevation view of a data storage system in a normal operating mode.  
     [0020]FIG. 10 is schematic cross sectional elevation view of a data storage system in a fall back operating mode.  
     [0021]FIG. 11 is a block diagram of a data storage system central control unit and two cartridge handling assemblies. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0022] The drawing, in general, illustrates a data storage system ( 10 ) comprising: a media picker displacement path ( 19 ) having a first end ( 17 ) and a second end ( 21 ); a first media picker assembly ( 50 ) mounted in the picker displacement path ( 19 ); a second media picker assembly ( 51 ) mounted in the picker displacement path ( 19 ); a plurality of data storage media access locations ( 40 ) located along the picker displacement path ( 19 ); the first media picker assembly ( 50 ) being displaceable along the path from the first end ( 17 ) to a point of interfering contact with the second media picker assembly ( 51 ); the second media picker assembly ( 51 ) being displaceable along the path ( 19 ) from the second end ( 21 ) to a point of interfering contact with the first media picker assembly ( 50 ).  
     [0023] Having thus generally described a data storage system  10 , various embodiments thereof will now be described in detail. One embodiment of a modular data storage system  10  is shown in FIG. 1 and comprises at least three modular units  12 ,  13 ,  14 . The modular units  12 ,  13 ,  14  are stackable vertically upon one another to form a compound housing assembly. While three modular units are shown in FIG. 1, it is to be understood that as few as three, or as many modular units as a customer desires, may be utilized in the modular data storage system  10 . Furthermore, one or more modular units may be added to the modular data storage system at any time. The modular data storage system  10  may also comprise cartridge (media) handling assemblies  50 ,  51  (generally referred to in the art as “picker assemblies” or “pickers”) which may be vertically translated along an open shaft  19  extending through the adjacent modular units  12 ,  13 ,  14  and having a first end  17  and a second end  19 , as described in further detail below.  
     [0024] In one embodiment the modular units  12 ,  13 ,  14  are substantially identical to one another, except where noted otherwise below. Each modular unit  12 ,  13 ,  14  may comprise a housing  30 ,  32 ,  34 , each having an upper opening, e.g.,  36  and a lower opening, e.g.,  38 . Each of the openings  36 ,  38  are sized and shaped to allow the cartridge handling assembly  50  to pass therethrough. Each intermediately positioned modular unit  13 , etc., i.e. all modular units except for the top most and bottom most units  12 ,  14  may further comprise a plurality of cartridge receiving devices  40  which may be, for example, magazines (e.g.,  42 ) or drives (e.g.,  44 ), or any combination thereof. The configuration of cartridge receiving devices  40  within each intermediate modular unit  13  need not be identical; each intermediate modular unit may be configured to suit a customer&#39;s particular needs.  
     [0025] As described elsewhere herein the top and bottom modules  12 ,  14  serve primarily as storage and access bays for the currently inactive picker assembly  50 ,  51 . Thus, the top and bottom modules  12 ,  14  may be identical to the intermediate module(s)  13 , etc. except that no cartridge receiving devices  40  would ordinarily be positioned therein.  
     [0026] The cartridge handling assembly  50  may be of the type described in U.S. patent application Ser. No. 09/045,134 filed 3/20/98 for MULTIPLANE TRANSLATING CARTRIDGE HANDLING SYSTEM of Gregg Schmidtke and Robert Mueller, now U.S. Pat. No. 6,025,972, issued Feb. 15, 2000, which is hereby incorporated by reference for all that is contained therein. FIG. 2 illustrates a modular unit  12  with most of the housing  30  broken away to more clearly show the cartridge handling assembly  50 . It is to be understood that the description below, except for the absence of cartridge receiving devices  40  in units  12  and  14 , may apply to all of the modular units (e.g.,  12 ,  13 ,  14 ) of the modular data storage system  10 .  
     [0027] As shown in FIG. 2, the cartridge handling (picker) assembly  50  may comprise a generally rectangular frame  16  having an upper portion  18 , a lower portion  20 , and four sides  22 ,  24 ,  26 ,  28 . Cartridge receiving devices  40  (magazines  42  and drives  44 ) are preferably accessible from at least one, and most preferably two or more, of the sides  22 ,  24 ,  26 ,  28 . The cartridge handling assembly  50  may also comprise a cartridge access device  52  capable of loading and retrieving the data cartridges (not shown) from the cartridge receiving devices  40 . Cartridge handling assembly  51  may be identical to cartridge handling assembly  50 . Z-fold ribbon cable (not shown) may be attached at one end to the top of the cartridge handling assembly  50  and extended out the top of the shaft  19  and attached at the other end to a control unit  400 , FIG. 11. A second Z-fold cable may be attached to the lower handling assembly  51  and extended out the bottom of shaft  19  to connect it to the control unit.  
     [0028] The modular data storage system  10  may also comprise a vertical lift system  58 , which is best shown in FIG. 2. The vertical lift system  58  may comprise a pinion gear assembly  60  mounted on the cartridge handling assembly  50 . The vertical lift system  58  may further comprise an actuator system  70  operably attached to the pinion gear assembly  60  for vertically translating the cartridge handling assembly  50  among the adjacent modular units  12 ,  13 ,  14  (FIG. 1). The vertical lift system  58  may further comprise a rack assembly (e.g.,  80 ) mounted on each of said modular units (e.g.,  12 ), which is operably associated with the pinion gear assembly  60 .  
     [0029] The pinion gear assembly  60  is preferably comprised of a first pinion gear  62  and a second pinion gear  64 , mounted diagonally opposite one another as shown in FIG. 2. Each pinion gear  62 ,  64  is preferably at least partially enclosed within a protective housing  66 ,  68 , respectively. The rack assembly  80  as shown in FIG. 2 is preferably comprised of a first rack  82  and a second rack  84 , mounted diagonally opposite one another and in alignment with the pinion gears  62 ,  64 , respectively. Each rack  82 ,  84  is fixedly attached to the modular unit housing  30 . The actuator system  70  is preferably comprised of a motor  72 , a gear/shaft assembly  74  to operably attach the motor  72  to the pinion gears  62 ,  64 , and a protective housing  76 . The actuator system protective housing  76  may be integrally formed with at least one of the pinion gear protective housings (e.g.  66 ), as shown in FIG. 2.  
     [0030] The actuator system  70  and pinion gears  62 ,  64  of the pinion gear assembly  60  are preferably fixedly attached to the cartridge handling assembly frame  16  at the upper portion  18  thereof. The actuator system  70  and pinion gears  62 ,  64  are preferably mounted diagonally as shown in FIGS. 1, 2 and schematically in FIG. 3 in order to most evenly distribute the weight thereof along the upper portion  18  of the frame  16 . The racks  82 ,  84  are also mounted diagonally as shown in this embodiment. FIGS. 4 and 5 illustrate alternate mounting positions for the actuator system, pinion gears and racks. As shown in FIG. 4, the actuator system  70 ′ may be mounted longitudinally, with the pinion gears  62 ′,  64 ′ being mounted longitudinally opposite one another and the racks  82 ′,  84 ′ also being mounted longitudinally opposite one another. As shown in FIG. 5, the actuator system  70 ″ may be mounted laterally, with the pinion gears  62 ″,  64 ″ being mounted laterally opposite one another and the racks  82 ″,  84 ″ also being mounted laterally opposite one another. Furthermore, the actuator system  70  may be mounted diagonally, longitudinally or laterally as shown in FIGS.  3 - 5  at either the upper portion  18  or the lower portion  20  (FIG. 2) of the frame  16 .  
     [0031] Referring again to FIG. 1, among adjacent modular units  12 ,  13 ,  14  there is an upper modular unit (e.g.,  12 ) and a lower modular unit (e.g.  13 ). The upper modular unit  12  comprises an upper rack assembly  80 , and the lower modular unit comprises a lower rack assembly  90 . FIG. 6 illustrates an upper rack  82  and a lower rack  92  from two adjacent modular units  12 ,  13 , respectively, and a pinion gear  62 . It is to be understood that the following description also applies to the second rack (e.g.,  84 ) of each rack assembly  80 ,  90  and also to the second pinion gear  64  of the pinion gear assembly  60 .  
     [0032] As shown in FIG. 6, the upper rack  82  comprises a plurality of gear teeth  100  having a predetermined pitch “P” (measured centerline-to-centerline), and the lower rack  92  also comprises a plurality of gear teeth  110  having the same predetermined pitch “P”. The upper rack  82  comprises a lowermost gear tooth  102 , and the lower rack  92  comprises an uppermost gear tooth  112 . In order for the pinion gear  62  to translate smoothly between the upper rack  82  and lower rack  92 , two conditions must exist. First, the adjacent modular units  12 ,  13  must be in substantial alignment. More specifically, the upper rack  82  of the upper modular unit  12  and the lower rack  92  of the lower modular unit  13  must be in substantial alignment (and, correspondingly, the upper rack assembly  80  and lower rack assembly  90  must be in substantial alignment). Second, as shown in FIG. 6, the distance “D” (measured the same way as “P”, i.e., centerline-to-centerline) between the lowermost gear tooth  102  of the upper rack  82  and the uppermost gear tooth  112  of the lower rack  92  must be equal to a multiple of the predetermined pitch “P”, in other words, P,  2 P, etc. Most preferably, and for the smoothest translation, D is equal to P. As shown in FIG. 6, there is preferably a space “S” between the upper rack  82  and the lower rack  92  so that the upper rack  82  and lower rack  92  do not abrade one another due to vibrations present during normal operation of the cartridge handling assembly  50  (FIGS. 1 and 2). For example, while the racks  82 ,  92  may each have a pitch “P” of approximately 6 mm, the spacing “S” may be approximately 0.5 mm.  
     [0033] The second cartridge handling assembly  51  may comprise a pinion gear assembly  60  identical to that described above in association with the first cartridge handling assembly  50 .  
     [0034] As described above, any number of modular units  12 ,  13 ,  14  may be stacked vertically upon one another to form adjacent modular units of a modular data storage system  10 , FIG. 1. The rack assemblies (e.g.  80 ,  90 ) may be aligned using an alignment tool (not shown) and shifting either the lower adjacent modular unit  13  or the upper adjacent modular unit  12  until the rack assemblies are aligned. Then, the lower modular unit  13  may be fixedly attached to the upper modular unit  12  using any conventional attachment means such as screws or the like. The distance “D” and spacing “S” are maintained between the upper and lower racks  82 ,  92  (and upper and lower rack assemblies  80 ,  90 ) because of the position of the racks  82 ,  92  within each modular unit housing  30 ,  32 .  
     [0035] In an alternative embodiment shown in FIG. 7, the modular units  212 - 217  of the modular data storage system  210  are placed within a conventional rack mount housing  220 . The housing  220  may comprise a plurality of attaching devices  222 , such as the L-shaped brackets shown in FIG. 7, which are adapted to fixedly attach the modular units  212 - 217  to the housing  220 . The attaching devices  222  may be fixedly attached to the rack mount housing  220  using a screw or the like. Each of the modular units  212 - 217  may be inserted into the rack housing  220  and then fixedly attached to several of the attaching devices  222  screws or the like. It is to be understood that, while L-shaped brackets are shown in FIG. 7, any conventional attaching device may be used to attach the modular units to the rack mount housing, as long as the attaching device does not interfere with the vertical translation of the cartridge handling assemblies  50 ,  51  among the adjacent modular units. The modular units  212 - 217  may alternatively be directly attached to the rack housing  220 . The size of the rack mount housing  220  (and number of attaching devices  222  the housing  220  can accommodate) may be determined in accordance with a customer&#39;s requirements. The modular units may have front covers or bezels mounted over the front faces thereof such as described in U.S. patent application Ser. No. 295,491, filed Apr. 20, 1999 for BEZEL ASSEMBLY AND METHOD OF PRODUCTION of Wayne E. Foslien, Joseph M. White, and Seiya Ohto, now U.S. Pat. No. 6,183,053, issued Feb. 6, 2001, which is hereby specifically incorporated by reference for all that is disclosed therein.  
     [0036] It can be seen from the above description that each of the modular units may have many common components, such as the housing, racks, drives and magazines. In addition, identical redundant cartridge handling assemblies  50 ,  51  may be used, one at a time in alternative operating modes, to access the drives and magazines of all of the intermediate modular units (e.g.  13 , or  213 - 216 ), as well as any further intermediate unit that may be subsequently added. This replication of components provides many advantages to the manufacturer as well as low-end, mid-range, and high-end customers, since a single set of components could be used to supply an entire family of data storage systems. FIG. 7 shows operation in the fall back operating mode after picker assembly  51  has failed and has descended due to the force of gravity into housing unit  217 . Picker  50  is shown operating to move cartridge receiving devices mounted in intermediate housing units  213 - 216 .  
     [0037] Having thus described two specific data storage system embodiments  10  and  210 , operation of each will now be explained with reference to a data storage system  300  shown schematically in FIGS.  8 - 10 .  
     [0038] As best shown by FIG. 8, the data storage system  300  comprises a cartridge receiving portion  308  having a plurality of cartridge receiving devices  310 ,  312 ,  314 ,  316 ,  318 ,  320  therein. A first picker storage bay  330  is mounted at a first end  332  of the cartridge receiving portion  308 . A second picker storage bay  340  is mounted at a second end  342  of the cartridge receiving portion  308 . An unobstructed picker displacement path  350 , which may be a vertical shaft having a central longitudinal axis XX extends through the cartridge receiving portion  308  and has opposite first and second terminal ends  352 ,  354  defined by the first and second picker receiving bays  330 ,  340 .  
     [0039] First and second cartridge handling assemblies or pickers  360 ,  362  are displaceably mounted in the picker displacement path  350 . The cartridge receiving devices  310 ,  312 ,  314 , etc. are arranged in vertically stacked layers defining tiers within the cartridge receiving portion  308  of the data storage system  300 . The picker bays  330 ,  340  also define top and bottom tiers of the data storage system which comprises first, second, third, fourth and fifth tiers  381 ,  382 ,  383 ,  384 ,  385 . The tiers may each be associated with a separate housing module such as shown in FIGS.  1  and  7  or, alternatively, may all be provided in a single non-modular housing.  
     [0040] In a pre-start up operating mode a second picker  362  with feedback unit  361  is positioned in the second picker storage bay  340  and a first picker  360  with feedback unit  359  is positioned in the fourth tier  384 , resting on top of the second picker, FIG. 8. This will typically be the position of the pickers when the data storage system  300  is in storage or when it is shipped to a customer. Each picker  360 ,  362  is operably connected such as by Z-fold ribbon cable, to a central control unit  400 , FIG. 11, which receives a position feedback signal therefrom such as by an associated motor encoder  359 ,  361  or the like. Control unit  400  sends control signals to assemblies  360 ,  362  to actuate each associated drive unit to vertically displace each handling assembly to a desired position.  
     [0041] At system start up the first picker  360  is driven by an associated drive assembly, such as described above with reference to FIG. 2, to a location inside the first picker storage bay  330  as shown in FIG. 9. It then remains in this position during normal operation of the data storage system  300 . In one implementation the first picker  360  remains in a power-on state at all times after system start up and is maintained at the position shown in FIG. 9 by force applied by its associated vertical lift drive assembly. In another implementation a gate or lock device  364  is mounted at a lower portion of the first picker storage bay  330  and allows the first picker to pass it without resistance on the way up  370  but prevents the picker from moving down  372  once it has entered the bay  330 . ( However the gate  364  may be selectively tripped by a gate release device  366  to enable the picker  360  to leave the bay  330  to commence a fall back operating mode as described below.) After system startup the second picker assembly  362  has access to all of the cartridges (not shown) received in the cartridge receiving devices  312 ,  314 ,  316 , etc in tiers  382 - 384  and may selectively move cartridges between the various receiving devices.  
     [0042] If the second picker  362  malfunctions and loses power it will descend, due to gravity, into the second picker storage bay  340 , as shown in FIG. 10. A sensing assembly  361  within the system, such as a drive motor encoder or current sensor senses the loss of power to the second picker  362  and in response thereto actuates the first picker  360  for required cartridge handling operations of the system. In the implementation in which a gate  364  is used to hold the first picker in its storage bay during normal mode operation, the gate tripper  366  is actuated after power loss to the second picker is sensed. The tripper thus releases gate  364  allowing the now powered first picker  360  to leave storage bay  330  and commence operation in the fall back mode. In the implementation wherein the first picker  360  is constantly powered no such gate or gate release mechanism needs to be actuated.  
     [0043] The second storage bay  340  is preferably constructed and arranged so that the second picker assembly  362  may be readily removed therefrom while the system  300  is operating in the fall back mode. The second picker assembly  362  may thus be replaced by another picker assembly or may be removed, repaired and reinstalled so that the system  300  may be returned to the above described normal mode of operation with a redundant picker.  
     [0044] Although an implementation of system  300  has been described above in which shaft  350  is vertical, it is to be understood that system  300  could also be implemented in a configuration identical to that described above in which shaft  350  is inclined or positioned horizontally. In such configurations gravity may not act on picker  362 , or may be insufficient to move it into bay  340  when it loses power. However, the first picker  360  can be used, in an initial operation in the fall back operating mode, as a pusher device to push picker  362  into bay  340 . Alternatively picker  362  could be provided with a small rechargeable battery operated backup drive motor  390 , or other drive device, which is actuated upon failure of the main drive assembly to drive the second picker assembly  362  into the second picker storage bay  340 .  
     [0045] It is also to be understood that the cartridge receiving portion  308  of the data storage system  300 , either including or excluding the picker storage bays  330 ,  340  may be implemented as a series of attached modular units, such as described with reference to FIGS.  1 - 7 , or as a single housing unit which is not separable into different modules.  
     [0046] While illustrative and presently preferred embodiments of the invention have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art.