Abstract:
An indicator light, such as an LED, for a computer disk drive module is controlled via an external controller. The disk drive module monitors a disk drive and determines a desired state of the LED, such as on, off or flashing, to indicate a status of the disk drive. The disk drive module provides a modulated signal carrying data that identifies the desired state on a path coupled to the indicator light and a terminal that is accessed by the external controller. The controller implements an algorithm for driving the indicator light, where the algorithm receives, as a first input, the desired state determined from the demodulated signal and, as a second input, information obtained from monitoring the disk drive module. The controller itself may obtain this information or receive it from a higher-level system controller.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates generally to the field of computer systems and, more specifically, to a technique for driving an indicator light for a disk drive module.  
         [0003]     2. Description of the Related Art  
         [0004]     Computer disk drives commonly use indicator lights such as light-emitting diodes (LEDs) to indicate a status of the drive. Information regarding a status of the disk can be conveyed by turning the light on or off in a steady or flashing manner. For example, the light may be off when the drive is unpowered or being powered up, and therefore unavailable for use. The light may be on steady when the drive has powered up with no errors and is ready for use. The light may flash in various on-off sequences to indicate that the disk is in use writing or reading data, that there has been a power loss or other fault condition, or other status information regarding the drive.  
         [0005]     Disk drives used for some storage servers and other computer devices may not have built-in indicator lights. Instead, one or more indicator lights may be provided on the second level packaging. For example, the indicator light may be located on the backplane of the disk drive enclosure. In a Fibre Channel storage enclosure, for instance, lightpipes can be run from the backplane to the front of the disk drives, such as the front of each hard disk drive bezel, via the disk drive module carrier to allow the operator to easily view the indicator lights. However, this approach is problematic as technology migrates toward small form factor (SFF) disk drives, such as 2.5-inch disk drives, from the current 3.5-inch drives. In this case, there is insufficient space for a lightpipe from each disk drive module carrier to be implemented since multiple hard disk drives are packaged within a carrier or substructure. Maintaining the indicator lights on the backplane is impractical since the operator cannot easily view them.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     The present invention provides apparatuses for addressing the above and other issues by providing a mechanism to share control of an indicator light over a single signal path.  
         [0007]     In one aspect of the invention, a disk drive and controller assembly includes a disk drive module including a disk drive, a circuit for monitoring the disk drive, and a conductive path extending from the circuit to an indicator light and to a terminal that is accessible external to the disk drive module. The circuit provides, via the conductive path, and responsive to the monitoring, a modulated signal identifying a desired state of the indicator light. A controller, external to the disk drive module, is provided for receiving the modulated signal from the disk drive module via the terminal, demodulating the modulated signal to determine the desired state, and implementing an algorithm for driving the indicator light. The algorithm receives, as a first input, the desired state determined from the demodulated signal and, as a second input, information obtained from monitoring the disk drive module.  
         [0008]     In a further aspect of the invention, a disk drive module includes a disk drive, a circuit for monitoring the disk drive, and a conductive path extending from the circuit to an indicator light and to a terminal that is accessible external to the disk drive module. The circuit provides, via the conductive path, a modulated signal identifying a desired state of the indicator light responsive to the monitoring. The modulated signal is provided with a pulse width time that is sufficiently small so that the indicator light is not perceived by a human as being illuminated by the modulated signal, by itself.  
         [0009]     In yet another aspect of the invention, a controller for a disk drive module includes a first circuit, external to the disk drive module, for receiving from the disk drive module, via a terminal of the disk drive module that is accessible external to the disk drive module, a modulated signal identifying a desired state of an indicator light in the disk drive module, demodulating the modulated signal to determine the desired state, and implementing an algorithm for driving the indicator light. A second circuit, which is in the disk drive module, monitors the disk drive and provides the modulated signal, via a conductive path in the disk drive module extending from the second circuit to the indicator light and to the terminal, responsive to the monitoring. The algorithm receives, as a first input, the desired state determined from the demodulated signal and, as a second input, information obtained from monitoring the disk drive module. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     These and other features, benefits and advantages of the present invention will become apparent by reference to the following text and figures, with like reference numbers referring to like structures across the views, wherein:  
         [0011]      FIG. 1  illustrates an arrangement for controlling an indicator light of a disk drive module, where multiple signal lines are needed across a backplane/controller card connector; and  
         [0012]      FIG. 2  illustrates an arrangement for controlling an indicator light of a disk drive module according to the invention, where only a single signal line is needed across a backplane/controller card connector. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]      FIG. 1  illustrates an arrangement for controlling an indicator light of a disk drive module, where multiple signal lines are needed across a backplane/controller card connector. One approach to packaging indicator lights such as LEDs is to provide the disk drive module itself with the indicator lights. However, this necessitates some type of shared access to control the states of the indicator lights.  FIG. 1  illustrates a disk drive module  100 , backplane  120  with indicator light  130 , and a controller  140 . A disk drive module generally refers to a structural carrier or housing that the disk drive electronics are provided within. One or more disk drive modules are typically installed into a higher-level assembly, such as a chassis, in a computer system such as a storage server. For example, in the IBM Enterprise Storage Server (ESS), eight-packs of disk drive modules are installed together. The disk drive module is installed into a backplane of the chassis. A latch in the front of the module locks it in place. The disk drive module is a field replaceable unit that can be quickly replaced if repair or replacement is needed. Other components such as controller cards can be installed in the backplane as well.  
         [0014]     Each indicator light can be illuminated by the disk drive module  100  generating a signal from the hard disk drive electronics  105  through its driver  110 , and through its connector  115  and the mating backplane connector  125 , through the backplane wiring and a further connector  135 , and into the controller card  140  via its connector  145 . The controller card  140  receives the signal from the disk drive module  100 , and generates a subsequent signal based on the disk drive&#39;s signal as well as internal controller card logic implemented in the electronics  155 . The subsequent signal is driven onto the backplane  120 , via the driver  160  and connector  145 , and connected to the indicator light  130  which, in turn, is appropriately activated, sending optical signals through the light pipes to the front of the disk drive module  100 .  
         [0015]     In particular, the disk drive module  100  does not directly turn the indicator light  130  on and off by generating a signal, signal A, that is wired to the backplane  120 /disk drive connector  115 . Instead, signal A is wired through the backplane  120  to the controller electronics  155 , where the controller generates a subsequent signal, signal B, that is directly related to the disk drive&#39;s incoming signal or that is related to the controller&#39;s desired behavior of the light indicator  130 . In either case, a signal is sent back to the backplane  120 , where it is connected to one or more backplane LEDs  130 . Lightpipes within the disk drive carrier carry the light information from the backplane LED to the front bezel of the disk drive. Note that for each LED, two signals (signal A and signal B) must cross the backplane/controller card connector  135 ,  145  on separate signal paths. For typical state of the art enclosures (e.g., with sixteen disk drive modules), thirty-two signal lines are required.  
         [0016]     One option is to employ embedded LEDs within the carrier, allowing the LED signal path to be much more straightforward. However, one shortcoming of this approach is that the LED signal is kept local to the disk drive module, so there is no clear way for the external controller card  140  to affect the LED state.  
         [0017]      FIG. 2  illustrates an arrangement for controlling an indicator light of a disk drive module according to the invention, where only a single signal line is needed across a backplane/controller card connector.  FIG. 2  illustrates a disk drive module  200  including electronics/circuitry  205 , a driver  210 , an indicator LED  230 , and a connector or terminal  215 . The indicator light  230  can be internal or external to the disk drive module  200 . A backplane  220  includes connectors or terminals  225  and  235 . A controller  240  includes a connector or terminal  245 , a receiver (Rcv)  250 , electronics/circuitry  255 , and a driver (Drv)  260 .  
         [0018]     In a particular embodiment, a single LED control signal for Fibre Channel Arbitrated Loop (FC-AL) disk drives (also part of the SFF-8045 Fibre Channel specification) can be used. Custom drive firmware and/or microcode can be implemented in the disk drive electronics/circuitry  205  to modulate the LED control signal to carry information regarding a desired state of the LED. The disk drive electronics/circuitry  205  can include a microprocessor, ASIC or other control device. Three major LED states are: 1) off, 2) on solid, and 3) on blinking. Complementary enclosure electronics  255  can be implemented in the controller card  240  to sense this modulation and remodulate the control signal so as to properly manage the LED on, off and blinking states. In this case, both the disk drive module  200  and the controller  240  control the state of the LED  230 .  
         [0019]     The electronics/circuitry  205  of the disk drive module provides a signal A ( 207 ) on signal path  212  with a frequency F 1  and pulse width Ta. The cathode/common wire of the LED  230  may be coupled to the signal path  212  so that a high voltage signal maintains the LED  230  in the off state, while a low voltage signal turns the LED  230  on. Other indicator lights such as incandescent lamps or other polarized light transmitters may also be used. Signal B ( 252 ) at the controller  240  is similar to signal A ( 207 ). Signal C ( 257 ) is the signal output from the electronic/circuitry  255  of the controller  240 , and has a frequency F 2  and pulse widths Tb and Tc as indicated. Signal D ( 224 ) on signal path  222 , which is the signal that controls the LED  230 , is a superposition of signal A ( 207 ) and signal C ( 257 ). A low voltage pulse duration of 30 msec. is indicated as an example.  
         [0020]     The disk drive module  200  itself does not directly control the LED  230 , but it communicates the desired LED state to the controller  240  by modulating the shared LED signal at a rate of F 1 . Each desired state of the indicator light is identified by a unique F 1  frequency (see signal A). F 1  should be sufficiently faster than F 2 / 2  in order for the controller electronics  255  to be able to correctly decode the modulated signal B. Thus, the modulated signal should be provided at a frequency that is sufficiently faster than a frequency at which the controller  240  drives the indicator light  230  so that the modulated signal can be demodulated by the controller  240 . Different blink rates can be accommodated by defining additional F 1  rates. Note that the pulse width time of signal A should be sufficiently small such that the LED  230  is not perceived by a human as being illuminated by signal A ( 207 ) alone. Thus, the modulated signal should be provided with a pulse width time that is sufficiently small so that the modulated signal is not perceived as being illuminated by the modulated signal, by itself. The user can only perceive when the LED  230  responds to low frequency signals, but not a short/fast pulse.  
         [0021]     The controller electronics  255  monitor the incoming modulated signal (signal B) only during specific time windows (Tc). To achieve this, the “enable A” signal to the receiver (Rcv)  250  controls when the electronics  255  receive an input, while the “enable B” signal controls when the driver (Drv)  260  provides an output. Once the controller  255  has decoded signal B, it transmits signal C. There may be some hysteresis built into the decoding algorithm. That is, the controller  140  may be constantly monitoring signal B. When a change is detected, the controller  140  waits a fixed amount of time for signal B to stabilize. This can also be considered debouncing the signal, in a sense.  
         [0022]     To turn the LED off, signal C can be a static DC high level (i.e., Tb=0). To turn the LED on solid, signal C can alternate at a frequency F 2  and a duty cycle of Tb/Tc so as to be visible to the human eye as a solid on indication (e.g., F 2 =60 Hz and Tb/Tc=50%). Similarly, to blink the LED, signal C can alternate at a frequency of F 2  and a duty cycle of Tb/Tc so as to be visible to the human eye with the predescribed blink rate (e.g., F 2 =2 Hz and Tb/Tc=50%). Generally, both steady on and blinking are achieved by causing the Signal D to oscillate at some frequency F 2 . The faster rate, e.g., 60 Hz, is so fast that the eye perceives the LED as being solid on when, in fact, it is just blinking faster than the eye can perceive. When F 2  is slowed down to below, e.g., 30 Hz, such as 2 Hz, the eye starts to perceive the light as pulsating or blinking. According to the invention, only a single signal (signal D) is required to be wired through the backplane. This is especially advantageous for the Fibre Channel standard, which allows only one signal path output from the disk drive module  200 .  
         [0023]     In one possible approach, a higher-level system controller  270  may communicate with the electronics/circuitry  205  of the disk drive module  200 , via a connector  202 , to instruct the disk drive module  200  to read or write data, for example. The system controller  270  maintains its own status information regarding the disk drive module  200 , e.g., to determine when there is a fault at the disk drive module  200 . For instance, the system controller  270  may learn that there is a fault at the disk drive module  200  when it instructs it to store data, but does not receive a confirmation signal back from the disk drive module  200  within a set amount of time. The system controller  270  can also communicate with the controller  240  of the disk drive module  200 , specifically with the electronics/circuitry  255 , via a connector  262 , to inform it of the fault or other status information regarding the disk drive module  200 .  
         [0024]     In another possible approach, the controller  240  itself performs the functions of the higher-level system controller  270  discussed above, e.g., in obtaining system level information about the disk drive condition. Specifically, the controller  240  may communicate with the electronics/circuitry  205  of the disk drive module  200 , via the connector  202  and communication path  280 , to instruct the disk drive module  200  to read or write data, for example. The controller  240  maintains its own status information regarding the disk drive module  200 , e.g., to determine when there is a fault at the disk drive module  200 .  
         [0025]     The electronics/circuitry  255  can implement an algorithm, e.g., by executing custom firmware and/or microcode, to determine how to drive the LED  230 . The electronics/circuitry  255  can include a microprocessor, ASIC or other control device. This algorithm can receive the desired indicator light state information from the disk drive module  200  as one input, and the status information obtained from monitoring the disk drive module, e.g., from the controller  240  itself or from the system controller  270 , as another input. The electronics/circuitry  255  can essentially override the desired state in driving the indicator light  230  when the algorithm determines that the desired state conflicts with the information obtained from monitoring the disk drive module  200 . For example, the disk drive module  200  may set the desired state to steady on, indicating no faults are present. If the information obtained from monitoring the disk drive module  200  indicates that there is a fault present, the electronics/circuitry  255  can set the LED  230  to an appropriate blinking state that identifies the fault. The controller  240  can also drive the indicator light consistent with the desired state when the algorithm determines that the desired state does not conflict with the information obtained from monitoring the disk drive module  200 . For example, the disk drive module  200  may again set the desired state to steady on, indicating no faults are present. If the information obtained from monitoring the disk drive module  200  also indicates that there are no faults present, the electronics/circuitry  255  can set the LED  230  to the desired steady on state. The invention thus allows the controller  240  to implement additional intelligence and decision-making criteria beyond that provided by the disk drive module  200  in determining how to drive the indicator light  230 .  
         [0026]     The invention has been described herein with reference to particular exemplary embodiments. Certain alterations and modifications may be apparent to those skilled in the art, without departing from the scope of the invention. The exemplary embodiments are meant to be illustrative, not limiting of the scope of the invention, which is defined by the appended claims.