Abstract:
A portable carrier for a disk drive including power control circuitry to enable a hot-plug connection between an external connector on the carrier and an opposing carrier mating connector on the back panel of an enclosure of a data storage system of the kind that is typically part of a file server, so that the disk drive can be powered from 5 and 12 volt power buses within the enclosure, but without damaging the disk drive or the opposing connectors at the moment of contact therebetween as a consequence of a current surge. The power control circuitry includes a timer and 5 volt and 12 volt carrier power switches (e.g., MOSFETs) that are respectively connected between the 5 volt and 12 volt power buses of the enclosure and the disk drive. Following a particular time delay, the timer generates an ENABLE signal to cause the carrier power switches to be rendered conductive to thereby complete current paths between the 5 volt and 12 volt power buses and the disk drive so that the disk drive can operate normally and communicate with a host computer of the data storage system.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to power control circuitry located on a portable carrier for a hot-pluggable disk drive which avoids damage to the disk drive and its connector by minimizing the effects of current surges when the disk drive is first coupled to a mating connector at the back panel of a data storage system enclosure within which power buses are housed.  
         [0003]     2. Background Art  
         [0004]     Hard disk drives of a data storage system are generally hot-pluggable. Therefore, it is not necessary to power down the entire system to install a disk drive that has been returned following the repair or replacement of a defective drive. The data storage system is typically part of a file server which is connected to a network at all times. All of the disk drives of the system and their associated electronics, including the power supplies to the drives, the host interface I/O boards, drive status indication electronics, disk array modules, etc. are housed in a metal enclosure (i.e., a data storage system chassis). A data storage system chassis contains a number of removable disk drive carriers, each carrier receiving a respective disk drive. The carrier protects the installed disk drive and ensures that the drive will be properly coupled to a mating connector which is located at the back panel or back plane of the system. The number of mating connectors at the back panel of the chassis is the same as the number of disk drives to be installed within the data storage system chassis.  
         [0005]     The back panel also has connectors to be mated to incoming disk drive carriers. At the instant that a disk drive carrier makes electrical contact with its respective connector at the back panel to power the disk drive within the carrier, there is a surge of current due to the fact that current is suddenly drawn from the power supply system at the back panel to charge the decoupling capacitors associated with the disk drive. Such a surge of current during the moment of contact is known to generate an electric spark which may damage the power pins of the disk drive carrier and/or the disk drive thereof as a consequence of the sudden rush of current flowing therethrough. Moreover, the corresponding high temperature that is generated by the electric spark can damage the disk drive as well as its mating connector at the back panel.  
         [0006]     To overcome the problem caused by the surge of current during the moment of hot-plugging the disk drive carrier to a back panel, disk drives have been manufactured that are adapted for current suppression during hot-plug applications. That is, when they are connected to a specially designed back panel which is capable of supporting hot-pluggable disk drives, the current surge is reduced to a level which will not damage the power pins of the disk drive connector and the corresponding power pins of the carrier mating connector at the back panel. By way of example, disk drives which are particularly adapted to be hot-pluggable include SCSI, Fiber Channel, Serial ATA and Serial Attached SCSI.  
         [0007]     In general, a hot-pluggable disk drive includes a connector having both long and short pins. The long pins are the power pre-charge pins and their respective ground pins are used to return the pre-charge current back to the power sources at the back panel. The short pins are used for the signals, powers and grounds. The same type of long and short pin hot pluggable mating connectors are located at the back panel, but with an opposite gender used for mating to their respective disk drives. In addition, the back panel is implemented with current limiting circuitry in electrical series with each of the pre-charge pins. The current limiting circuitry prevents the electrical sparks at the pre-charge pins when contact is first made between the pre-charge pins of the disk drive connector and the pre-charge pins at the back panel mating connector.  
         [0008]     By way of particular example, and referring to  FIG. 1  of the drawings, there is shown a block diagram to illustrate the present technique for solving the current surge problem that is faced by disk drives used in hot-plug applications.  FIG. 1  depicts the back panel or back plane  1  of a data storage enclosure or chassis. In the present example, the back panel  1  accommodates 1 . . . N FC (i.e., Fiber channel) disk drives  3 . Each disk drive  3  is mounted in a portable disk drive carrier  5 . The connector  7  of each disk drive  3  is mated to a respective disk drive connector  9  at the back panel  1 . Connectors  7  and  9  are identical in construction, but of opposite gender.  
         [0009]     The opposing disk drive connectors  7  and  9  of the disk drive  3  and back panel  1  are especially adapted for hot-plug applications. As described above, each connector  7  and  9  includes sets of long and short pins that are interconnected with respective power buses at back panel  1 . The long pins of disk drive mating connector  9  include a 5 volt pre-charge pin  10 , a 12 volt pre-charge pin  12 , and a ground pre-charge pin  14 . The long 5 volt pre-charge pin  10  is connected to the 5 volt power bus  16  of the data storage system via 5 volt pre-charge current limiting circuitry  18 . The long 12 volt pre-charge pin  12  is connected to the 12 volt power bus  20  of the system via 12 volt pre-charge current limiting circuitry  22 . The long ground pre-charge pin  14  is connected directly to the ground bus  24  of the system.  
         [0010]     The current limiting circuitry  18  and  22  are connected to the 5 volt and 12 volt power buses  16  and  20  to limit the current flowing through their respective long pre-charge pins  10  and  12 . In particular, the 5 volt pre-charge current charges up the 5 volt decoupling capacitors of the disk drive  3  to 5 volts prior to the time that the short 5 volt power pin  26  of the system makes contact with its complementary pin at the disk drive connector  7 . Likewise, the 12 volt pre-charge current charges up the 12 volt decoupling capacitors at the disk drive  3  to 12 volts prior to the time that the short 12 volt power pin  28  of the system makes contact with its complementary pin at the disk drive connector  7 .  
         [0011]     The short pins at the disk drive mating connector  9  at back panel  1  include the aforementioned 5 volt system power pin  26 , the aforementioned 12 volt system power pin  28 , a ground pin  30 , and the disk drive signal interface pins (not shown). The short pins  26 ,  28  and  30  of disk drive mating connector  9  are connected to their complementary short pins at the disk drive connector  7  after the long pins  10 ,  12  and  14  have first been connected to their complementary long pins of disk drive connector  7 . In general, the long 5 volt pre-charge pin associated with the disk drive connector  7  is connected directly to the short 5 volt power pin, and the long 12 volt pre-charge pin at connector  7  is connected directly to the short 12 volt power pin. Therefore, unlike the pins of disk drive mating connector  9 , there is no current limiting circuitry between the pre-charge pins and their respective power pins of the connector  7  at the incoming disk drive side.  
         [0012]     By virtue of the difference in length between the opposing long (e.g.,  10 ,  12  and  14 ) and short (e.g.,  26 ,  28  and  30 ) pins, the decoupling capacitors at the disk drive side will be fully charged to their respective voltage levels (e.g., 5 volts and 12 volts) during the initial contact of the long pre-charge pins. Moreover, since the long pre-charge pins and the short power pins at the disk drive side are connected directly together, the short power pins will also receive their full voltage levels.  
         [0013]     By the time that the short power pins at the incoming disk drive side make contact with their complementary short power pins of the mating disk drive connector  9  at the back panel  1 , the short power pins at the disk drive side will have already been charged to their respective voltage levels. Since the voltage levels on the short power pins at the incoming disk drive side and the complementary short power pins (e.g.,  26 ,  28  and  30 ) at the mating disk drive connector  9  are identical (e.g., 5 volts, 12 volts, or ground), there will be no voltage difference and, therefore, no current flowing through the complementary pairs of short power pins at the instant of contact between the incoming connector  7  of disk drive  3  and its opposing mating connector  9  at the back panel  1 . In this case, the disk drive  3  will not begin to draw current from the 5 volt and 12 volt power pins to sustain normal operation until a short time after the initial contact is made between the opposing incoming and mating disk drive connectors  7  and  9 .  
         [0014]     In some cases, there will be a small amount of current surging through the complementary pairs of short power pins at the instant of contact between the connector  7  of disk drive  3  and its opposing mating connector  9  at the back panel  1 . This is due to the resistance at the short power pins at the drive connector  7  being greater than the resistance at the pre-charge pins at the drive connector  7 . Thus, the short power pins have slightly lower voltages than the voltages at their respective pre-charge pins. However, in most cases, this small amount of inrushing current will not have enough energy to generate electrical sparks to damage the power pins at the drive connector  7  and at the mating connector  9  at back panel  1  during the instant of contact. Therefore, the chances of damaging the disk drive  1  during the hot-plug process is greatly reduced.  
         [0015]     Despite the ability of the data storage system illustrated in  FIG. 1  to avoid current surges and corresponding pin damage during the hot-plug connection of the disk drives to their respective mating connectors at the back panel  1 , there are some data storage systems that require the integration of relatively low cost disk drives, such as a parallel ATA (PATA) drive, which are not capable of a hot-plug connection. In this same regard, the system of  FIG. 1  cannot handle some carriers which are required to accommodate a hot-pluggable disk drive along with I/O circuitry which is capable of transmitting input and output disk drive data but is not a part of the disk drive. By way of example, a Serial ATA (SATA) disk drive having a port selector may have to be located on the same disk drive carrier. Although the SATA disk drive, in and of itself, may be manufactured for hot-plug application, the I/O port selector which must be hot-plugged to the back panel is typically not capable of making a hot plug connection. Consequently, the connector contact pins of the SATA disk drive as well as the complementary contact pins of the opposing mating connector at the back panel may remain susceptible to damage due to current surges at the moment of interconnection therebetween. Yet another example where the solution of  FIG. 1  may prove to be ineffective is in the case where the disk drive carrier accommodates both a disk drive which is not adapted for a hot-plug connection and an electronic circuit which is not part of the disk drive. By way of example, such an independent circuit is a SATA-to-PATA converter circuit for a parallel ATA (PATA) disk drive.  
       SUMMARY OF THE INVENTION  
       [0016]     In general terms, power control circuitry is disclosed for a portable carrier within which a disk drive is housed to enable the hot-plug connection of the carrier within a data storage system enclosure (e.g., at the back panel thereof) of a data storage system of the kind that is typically part of a network file server. The power control circuitry delays the supply of power from power buses within the data storage system enclosure to the disk drive when an external connector of the disk drive carrier is detachably coupled to an opposing carrier mating connector at the back panel of the data storage system enclosure so as to avoid having to first power down the system and avoid damage to the disk drive and the opposing connector of the disk drive carrier at the back panel of the enclosure.  
         [0017]     The power control circuitry of the portable disk drive carrier is electrically connected between the external connector of the carrier and an internal disk drive mating connector of the carrier. In the preferred embodiment, a connector of the disk drive is attached to the internal disk drive mating connector of the carrier, whereby the power control circuitry and the disk drive are interconnected with one another. The power control circuitry includes a time delay circuit by which power is supplied from the power buses at the data storage system enclosure to the disk drive at the disk drive carrier a particular time after the external carrier connector of the disk drive carrier is first coupled to the carrier mating connector at the back panel of the data storage system enclosure.  
         [0018]     The time delay circuit of the power control circuitry includes a timer that is adapted to establish a time delay before power is supplied to the disk drive. The power control circuitry has 5 volt and 12 volt carrier switches (e.g., MOSFETs) that are respectively connected between 5 volt and 12 volt power buses at the storage system enclosure and the disk drive once the disk drive carrier is coupled to the back panel of the system enclosure. When the time delay has expired following the coupling of the external carrier connector of the disk drive carrier to the carrier mating connector at the back panel, the timer generates an ENABLE signal which is provided to each of the 5 volt and 12 volt carrier switches. The carrier switches are now rendered conductive to complete current paths between the 5 volt and 12 volt power buses and the disk drive to allow normal disk drive operation, whereby the disk drive can be accessed by the host computer. However, during the aforementioned time delay, any current surges that may have been generated when the disk drive carrier is first coupled to the back panel of the data storage system enclosure will be dissipated.  
         [0019]     In a preferred embodiment of the invention, the disk drive that is housed within the portable disk drive carrier is a parallel ATA (PATA) disk drive. The PATA disk drive is accessed by a serial ATA (SATA) host bus adapter (HBA) by way of an HBA connector at the data storage system enclosure. Therefore, a SATA-to-PATA converter circuit is located on the disk drive carrier to convert the serial differential signal of the SATA disk drive to parallel data that is associated with a PATA disk drive. The SATA-to-PATA converter circuit is powered from the 5 volt power bus at the storage system enclosure once the 5 volt carrier switch of the power control circuitry has been rendered conductive by the ENABLE signal generated by the timer following the expiration of the time delay. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  shows a data storage enclosure back panel and a disk drive carried by a standard portable disk drive carrier and adapted for conventional hot-plug applications;  
         [0021]      FIG. 2  shows a data storage enclosure back panel and a portable disk drive carrier according to the preferred embodiment of this invention having power control circuitry and a serial-to-parallel data converter by which the carrier is adapted for hot-plug applications while avoiding the occurrence of current surges and minimizing the damage associated therewith; and  
         [0022]      FIG. 3  shows details of the power control circuitry that is located on the disk drive carrier of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0023]      FIG. 2  of the drawings shows a portable disk drive carrier  40  having power control circuitry and a serial-to-parallel data converter, whereby the carrier  40  is adapted for hot-plug applications, while avoiding the problems described above while referring to  FIG. 1 . To accomplish the foregoing, the disk drive carrier  40  is interfaced with and hot-pluggable from a data storage enclosure back panel  42  that is adapted to accommodate carrier  40 . The disk drive carrier  40  of  FIG. 2  includes, for example, a parallel ATA (PATA) disk drive  44  having a disk drive connector  46  that is coupled to a corresponding disk drive mating connector  48  by which the disk drive  44  communicates with disk drive carrier  40 . However, it is to be understood that the disk drive  44  may or may not be capable of a hot-plug connection in and of itself. Except for repair or replacement, the disk drive  44  will remain housed within its carrier  40  at all times. Once installed, the disk drive  44  is not intended to be hot-pluggable from carrier  40 .  
         [0024]     The disk drive carrier  40  also includes an external carrier connector  50  to be detachably coupled to a corresponding carrier mating connector  52  at the back panel  42 . To enable hot-plug operation from the back panel  42  with the soon to be described advantages of the present improvement, the disk drive carrier  40  is provided with carrier power control circuitry  54  and serial-to-parallel (SATA-to-PATA) converter circuitry  56 .  
         [0025]     A host bus adapter (not shown) accesses the disk drive  44  that is installed on disk drive carrier  40  by way of a host bus adapter (HBA) connector  58  that is located on the data storage enclosure back panel  42 . In this case, the host bus adapter is a Serial ATA (SATA) adapter. Therefore, the carrier  40  is required to have the aforementioned SATA-to-PATA converter circuitry  56 . The HBA connector  58  communicates with the carrier mating connector  52  at back panel  42  by way of a SATA Tx and Rx bus  57 . Likewise, the SATA-to-PATA converter circuitry  56  communicates with the external carrier connector  50  of carrier  40  by way of an additional SATA Tx and Rx bus  59 . The SATA-to-PATA converter circuitry  56  also communicates with the internal disk drive mating connector  48  of carrier  40  by way of data and control buses  55 .  
         [0026]     Unlike the conventional hot-plug technique described while referring to  FIG. 1 , it is not necessary to have long pre-charge power pins at the disk drive mating connector (designated  9  in  FIG. 1 ) located at the back panel (designated  1 ) for charging up the corresponding long pre-charge power pins at the disk drive connector (designated  7 ). That is, in  FIG. 2 , the disk drive power pins are not directly connected to the complementary power pins at the back panel. The power pins of the disk drive connector  46  of disk drive  44  are otherwise connected to the power pins at the disk drive mating connector  48  rather than to the power pins of the external carrier connector  50 . In fact, the disk drive (e.g., PATA disk drive  44 ) may not even have long pre-charged power pins.  
         [0027]     The disk drive  44  of  FIG. 2  is powered from the output of the carrier power control circuitry  54  via the disk drive mating connector  48  and the opposing disk drive connector  46 . More particularly, the output of the power control circuitry  54  supplies the required power to the PATA disk drive  44  only after the external carrier connector  50  of the disk drive carrier  40  has been coupled to its opposing mating connector  52  at the back panel  42  and after the expiration of a predetermined time delay following the successful interface of carrier  40  with back panel  42 .  
         [0028]     As previously explained, the SATA-to-PATA converter circuitry  56  on disk drive carrier  40  is required in order for the PATA disk drive  44  to be accessed by the SATA host bus adapter at HBA connector  58 . A SATA host bus adapter is normally designed to interface (i.e., to communicate with and to store and retrieve disk data) to SATA disk drives rather than the PATA disk drive  44  as shown in  FIG. 2 . Therefore, the SATA-to-PATA converter circuitry  56  is necessary in this case to convert the serial differential signal of a SATA disk drive to the 16-bit parallel data of a PATA disk drive.  
         [0029]     The details of the carrier power control circuitry  54  associated with disk drive carrier  40  are now explained while referring concurrently to  FIGS. 2 and 3  of the drawings. As is best shown in  FIG. 3 , power control circuitry  54  includes a timer  60 , a 5 volt carrier power switch  70  and a 12 volt carrier power switch  80 . The timer  60  includes a timing device  62  and an oscillator  64 . The oscillator  64  provides the timing device  62  with a reference clock signal  66 .  
         [0030]     The 5 volt carrier power switch  70  of the carrier power control circuitry  54  includes a MOSFET transistor device  72  and a MOSFET driver  74 . The MOSFET driver  74  is coupled to MOSFET transistor device  72  to control the operation (i.e., state) thereof. As will soon be described, the MOSFET transistor device  72  functions as an electronic switch by which to enable 5 volt power to be supplied to disk drive  44  from the 5 volt system power bus at back panel  42  by way of the external carrier connector  50  of disk drive carrier  40 , the 5 volt power pin  97  thereof, a 5 volt carrier  90 , and the disk drive mating connector  48  that is coupled in mating engagement with the opposing disk drive connector  46 .  
         [0031]     The 12 volt carrier power control switch  80  of the carrier power control circuitry  54  also includes a MOSFET transistor device  82  and a MOSFET driver  84 . The MOSFET driver  84  is coupled to MOSFET transistor device  82  to control the operation (i.e., state) thereof. As will also be described, the MOSFET transistor device  82  functions as an electronic switch by which to enable 12 volt power to be supplied to disk drive  44  from the 12 volt system power bus by way of the external carrier connector  50  of disk drive carrier  40 , the 12 volt power pin  98  thereof, a 12 volt carrier  92 , and the disk drive mating connector  48  that is coupled in mating engagement with the opposing disk drive connector  46 .  
         [0032]     The carrier power control circuitry  54  provides two controlled output voltages from the 5 volt power switch  70  via the 5 volt carrier  90  and from the 12 volt power switch  80  via the 12 volt carrier  92 . The 5 volt carrier  90  feeds each of the installed PATA disk drive  44  and the SATA-to-PATA converter circuitry  56 , and the 12 volt carrier  92  feeds PATA disk drive  44 . With the disk drive carrier  40  coupled to the back panel  42 , a continuous ground path is established from the GND bus at back panel  42  to the PATA disk drive  44  by way of the ground power pins  96  and  99  of the opposing connectors  52  and  50  and a GND carrier  91  that runs between the power control circuitry  54  and disk drive  44 .  
         [0033]     The operation of the carrier power control circuitry  54  of disk drive carrier  40  is now disclosed while continuing to refer to  FIGS. 2 and 3  of the drawings. Unlike the conventional hot-plug technique illustrated in  FIG. 1 , the external carrier connector  50  of disk drive carrier  40  and the carrier mating connector  52  at the data storage enclosure back panel  42  do not require long pre-charge power pins. Thus, during the moment of contact between the external carrier connector  50  and its opposing carrier mating connector  52 , the current on the 5 volt power pin  94  and the current on the 12 volt power pin  95  of the carrier mating connector  52  of  FIG. 2  do not immediately flow through the carrier power control circuitry  54  of disk drive carrier  40 . In this case, both the 5 volt carrier power switch  70  and the 12 volt carrier power switch  80  of  FIG. 3  are initially disabled (i.e., the drivers  74  and  84  force MOSFET transistor switches  72  and  82  to an off or non-conductive state).  
         [0034]     Despite the 5 and 12 volt carrier power switches  70  and  80  being disabled during initial contact between the opposing connectors  50  and  52 , current will still flow into the timer  60  by way of the 5 volt power pin  94  of carrier mating connector  52  and the 5 volt power pin  97  of external carrier connector  50 . The magnitude of the 5 volt current flowing to timer  60  is small relative to the disk drive current (i.e., micro-amps on one hand and amps on the other). In this regard, the timer  60  is selected so as to be capable of operating at low voltage conditions (e.g., about half the 5 volts to be provided by power pins  94  and  97 ) and low current (e.g., about 200 microamps). Therefore, any current surge will be reduced to a level that is sufficiently low so as to avoid damaging the connector pins  94  and  97  at back panel  42  and disk drive carrier  40  during the initial contact therebetween. By way of example only, the timing device  62  of timer  60  is a commercially available timer, such as Part No. MIC1555 manufactured by Micrel, Inc. that is capable of operating at a low voltage (e.g., 2.7 volts) and a low current (e.g., about 200 microamps).  
         [0035]     When the input voltage at the 5 volt power pin  94  of carrier mating connector  52  rises to the operating voltage required by timer  60  (e.g., about 2.7 volts), the timing function is initiated. That is to say, the timing device  62  of timer  60  counts the number of reference clock signals  66  that are generated by oscillator  64  during a predetermined time. A suitable time (e.g., 1.0 seconds) to count the reference clock signals  66  is chosen to be sufficient to allow any bouncing motion of the contact pins at the opposing mating connectors  50  and  52  to subside.  
         [0036]     Prior to the time that the 5 volt and 12 volt power pins  97  and  98  of external carrier connector  50  reach their full voltage levels at the input to the 5 and 12 volt carrier power switches  70  and  80 , the timer  60  disables switches  70  and  80  by means of supplying a SW-DISABLE signal on signal line  100  to each of the MOSFET drivers  74  and  84 , whereby the MOSFET transistor switches  72  and  82  are turned off. The SW-DISABLE signal in this case is a low voltage TTL (transistor-to-transistor logic) signal.  
         [0037]     Following the elapsed time period (e.g., 1.0 seconds) during which the timing device  62  of timer  60  is counting reference clock signals  66 , the timer  60  supplies a high voltage SW-ENABLE TTL signal on signal line  100 , such that the 5 volt and 12 volt carrier power switches  70  and  80  are now enabled (e.g., MOSFET drivers  74  and  84  cause MOSFET transistor switches  72  and  82  to be turned on). In other words, drivers  74  and  84  generate a sufficient gate voltage, whereby MOSFET transistor switches  72  and  82  are now rendered conductive.  
         [0038]     Once the 5 volt and 12 volt carrier power switches  70  and  80  of the carrier power control circuitry  54  at disk drive carrier  40  have been enabled by the high voltage SW-ENABLE TTL signal on signal line  100 , the 5 volt and 12 volt carriers  90  and  92  are electrically connected (via respective carrier power switches  70  and  80 ) to the 5 volt and 12 volt power pins  97  and  98  of the external carrier connector  50  and to the corresponding 5 volt and 12 volt system power buses at back panel  42  via the 5 volt and 12 volt power pins  94  and  95  of the carrier mating connector  52 . Accordingly, the power that is required by the PATA disk drive  44  and the SATA-to-PATA converter circuitry  56  is now supplied to support normal disk drive operation.  
         [0039]     It may be appreciated that the power control circuitry  54  is located entirely on the portable disk drive carrier  40 . Therefore, when a repair to circuitry  40  is required, it is not necessary to power down the entire data storage system and to spend time making a time consuming disassembly as would be the case if the power control circuitry were otherwise located on the back panel  42  of the data system enclosure. By virtue of the present invention, it is only necessary to remove the defective disk drive carrier for repair or replacement without having to remove the back panel  42  to be sent out for service during which the entire system would remain disconnected from its network.