Abstract:
A method for managing power consumption by a network device is disclosed. The network device includes first and second ports, each of the first and second ports identified by a unique identifier and adapted to handle separate network traffic. The method includes verifying that the first and the second ports are connected to a common network end node; shutting off a link between the first port and the network end node; obtaining the unique identifier of the first port; creating, on the second port, a virtual port in response to the unique identifier of the first port; discovering the virtual port on the network device; and redirecting traffic formerly routed through the link through the virtual port.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to power management in network systems and more specifically to power management of a network device having multiple connections to a network fabric. 
       BACKGROUND OF THE INVENTION 
       [0002]    Power consumption is always a concern in managing an enterprise network system. A typical enterprise network, such as a storage network, may include a large number of network devices such as servers, switches, and storage devices. A number of those devices may be situated in a confined physical space. For example, multiple blade servers may be stacked in a single rack. During operation, electrical and mechanical components produce heat, which must be displaced to ensure proper functioning of the server components. In blade enclosures, as in most computing systems, heat may be removed with fans or reduced by the use of air conditioning. As servers become more powerful, more electricity is consumed by not only the servers but also the fans and/or the air conditioners needed to keep the servers cool. As such, it is desirable to find ways to reduce the power consumed by each network device without jeopardizing the operations of those devices or affecting their performance. 
       SUMMARY OF THE INVENTION 
       [0003]    In general, the present invention relates to systems and methods to reduce power consumption of a network device by using virtualization techniques to migrate connectivity to a shared port on the network device. 
         [0004]    Embodiments of the present invention utilize virtualization techniques to perform port migration on a network device. The virtualization techniques make it possible to encapsulate the characteristics of a first physical port and, based on the encapsulated characteristics, create a virtual port on a second physical port to perform the same functions of the first port. As a result, one or more power-consuming physical ports can be migrated to a single physical port. Those power-consuming ports can then be shut off to save power consumption by the device without losing any connectivity to other fabric-connected devices on the network. When it becomes necessary to switch to a powered-down physical port, or when Input/Output (I/O) bandwidth demand increases beyond the capacity of the single physical port, the same encapsulated characteristics can be re-applied to the first ports and those first ports can be reactivated to provide more bandwidth for the host server. 
         [0005]    In one embodiment, the World Wide Port Name (WWPN) and World Wide Node Name (WWNN) of the first physical port are first noted. Subsequently, an N-Port ID Virtualization (NPIV)-based virtual port on the second port is created using the WWPN/WWNN of the first port so that the newly created virtual port can assume the identity of the first port. The virtual port may then be discovered by the host server and log into all the appropriate target storage devices on the network. After the connectivity between the virtual port and the storage devices is reestablished, I/O traffic to the server is resumed and redirected to the virtual port. Because the virtual port has adopted the same WWPN/WWNN as the powered-down first port, the host server would not know that the physical communication channels for some of its communication has been changed, that a virtual port on the second port, instead of the first port, is now being used to connect to target device. As far as the server is concerned, there has been no change in connectivity to the network. As such, the first physical port can be safely shut down without impacting the connectivity of the hosting server. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a block diagram illustrating a conventional Fibre Channel network including a storage device with two dual-port Fibre Channel Host Bus Adapters (HBAs). 
           [0007]      FIGS. 2   a  and  2   b  illustrate the connections between an HBA and a fabric switch before and after port migration has been performed according to an embodiment of the invention. 
           [0008]      FIG. 3  is a flow chart illustrating the exemplary steps in migrating a physical port to another port using virtualization techniques according to an embodiment of the invention. 
           [0009]      FIG. 4  illustrates a redundant network adapted to utilize the power saving methods disclosed in embodiments of the invention. 
           [0010]      FIG. 5  illustrates an embodiment of a network adapter that may adopt the power saving methods disclosed in embodiments of the invention. 
           [0011]      FIG. 6  illustrates an exemplary host server according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]    In the following description of preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific embodiments in which the invention can be practiced. It is to be understood that other embodiments can be used and structural changes can be made without departing from the scope of the embodiments of this invention. 
         [0013]    In general, the present invention relates to systems and methods to reduce power consumption of a network device by using virtualization techniques to migrate connectivity to a shared port on the network device. Although the following embodiments of the invention are described specifically with reference to server-based HBAs, the methods and systems introduced herein can be extended to hardware environments other than those described below. Furthermore, though the embodiments are described for Fibre Channel networks, it should be understood that they can also be adapted for networks using other protocols, such as Fibre Channel over Ethernet (FCoE). 
         [0014]      FIG. 1  illustrates an exemplary Fibre Channel storage network. The Fibre Channel storage network includes a host server  100 , a fabric switch  106  and two storage devices  108 ,  110 . The host server  100  may be connected to the storage devices  108 ,  110  through the fabric switch  106 . Although only two storage devices  108 ,  110  are illustrated, it should be understood that additional storage devices may be a part of the network and connected to the host server  100 . The host server  100  includes two dual-port host bus adapters (HBAs)  102 ,  104 . Each of the dual-port HBAs  102 ,  104  has two separate physical Fibre Channel ports (not shown) designed to provide two communication channels to the other devices on the network. Other networks may use multiple single-port adapters each with one physical Fibre Channel port in place of a dual-port HBA. Regardless of what type of HBA is used, each port on the HBAs  102 ,  104  is identifiable by a unique WWPN and/or a WWNN and may be designed to be independent of one another. In the network illustrated in  FIG. 1 , the two dual-port HBAs  102 ,  104  may together provide four connections  112  to the fabric switch  106 . Each of these connections may be a full, physical connection that utilizes one of the physical FC ports on the HBAs  102 ,  104  and a dedicated optical fiber (or other physical transport means) connecting the HBAs  102 ,  104  to the fabric switch  106 . 
         [0015]    The fabric switch  106  may also include multiple ports (not shown) adapted to transmit and receive data from the host server  100 . The fabric switch  106  may be connected to at least one of storage devices  108 ,  110 . The fabric switch  106  may effectively determine, by the WWPNs associated with the ports on the host server  100  and the storage devices  108 ,  110 , the connections between the host server  100  and each of the storage devices  108 ,  110 . Although only one fabric switch  106  is illustrated in  FIG. 1 , it should be understood that the connections between the host server  100  and any one of the storage devices  108 ,  110  may go through multiple fabric switches. In other networks, the host server may be connected to different storage devices via different fabric switches. 
         [0016]    Because the illustrated host server  100  of  FIG. 1  has four separate connections  112  to the fabric switch  106 , power may be continuously consumed by all of the four physical Fibre Channel ports on the two HBAs  102 ,  104  of the server  100  when the server is in operation. Similarly, the corresponding ports on the fabric switch  106  also may always be in a powered-on mode. When the devices are turned on, power may be continuously consumed regardless of whether or not any of the communication channels between the host server and the fabric switch  106  are being used to transmit data. That is, not all the bandwidth available from all the channels  112  may be needed all the time. In fact, it is very often the case that some channels between the server  100  and the fabric switch  106  may carry no data at a particular time. Those channels may exist for redundancy/failover purposes. In other words, some of the ports (or adapters) are present merely as backups to other ports (or adapters). In other networks, some of the channels may be present only for peak demand purposes. During off-peak times, far less bandwidth than the full available bandwidth is needed by the applications on the host server  100 . This may be the case at night, when the usage of the network is typically much lower than during the day. Nevertheless, because all the ports in existing network devices are always on even when they are not actually in use for transmitting data, the amount of power consumed by the network during off-peak hours may not be any less than during peak usage. 
         [0017]    Because each HBA  102 ,  104  typically has its own power supply, to the extent that the HBA or portions of the HBAs (e.g., the individual Fibre Channel port) can be shut down for a certain period of time when the bandwidth provided by that HBA  102 ,  104  is not needed, some power may be saved. Accordingly, it may be beneficial to shut down ports that are not currently being utilized for carrying data to save power and reduce heat generation. However, simply shutting down an adapter or a port on the adapter and dropping the link between that adapter/port and the fabric switch  106  may not be desirable because it may cause the loss of connection to the storage devices connected to the fabric switch  106 . This in turn would cause loss of connection to the storage devices within the host server&#39;s operating system, creating a ripple effect that can yield unpredictable results from the perspective of applications running on the host server. 
         [0018]    Embodiments of the present invention utilize virtualization techniques to perform port migration on a network device. The virtualization techniques make it possible to encapsulate the characteristics of a first physical port and, based on the encapsulated characteristics, create a virtual port on a second physical port to perform the same functions of the first port. As a result, one or more power-consuming physical ports can be migrated to a single physical port. Those power-consuming ports can then be shut off to save power consumption by the device without losing any connectivity to other fabric-connected devices on the network. When it becomes necessary to switch to a powered-down physical port, or when Input/Output (I/O) bandwidth demand increases beyond the capacity of the single physical port, the same encapsulated characteristics can be re-applied to the powered-down ports and those powered-down ports can be reactivated to provide more bandwidth for the host server. 
         [0019]      FIGS. 2   a  and  2   b  illustrate, respectively, one of the HBAs of  FIG. 1  before and after port migration having been performed using virtualization techniques. First referring to  FIG. 2   a , one of the dual-port HBAs of  FIG. 1  is shown in greater detail here. The HBA  102  may include two independent physical Fibre Channel ports A and B  202 ,  204 . As illustrated in  FIG. 2 , both physical Fibre Channel ports A and B  202 ,  204  are in a powered-on mode. Each of the physical ports  202 ,  204  has a live connection to the fabric switch  208 , through which the host server (not shown in  FIGS. 2   a  and  2   b ) housing the HBA is connected to other devices, such as storage devices, on the network. However, as discussed previously, one of the physical ports (e.g., port  204 ) may be a failover for the other port (e.g., port  202 ). Alternatively, the HBA may not require the bandwidth provided by both physical ports  202 ,  204  at the same time. Thus, it is desirable to power down one of the physical ports by migrating the failover/unused physical port  204  to the active port. 
         [0020]    In one embodiment of the invention, virtualization techniques may be used to create a virtual port on a physical port  202  (i.e., the second port) to take on the role of another physical port  204  (i.e., the first port) connected to a common fabric.  FIG. 2   b  illustrates the dual-port HBA  102  of  FIG. 2   a  having completed a port migration process. As illustrated in  FIG. 2   b , the previously active channel between the second Fibre Channel port  204  and the fabric switch  106  has been powered down. Instead, a virtual instance  206  of the second physical port  204  may be created in physical port  202  through a virtualization process, which will be discussed in detail below. The virtual port  206  may share the same WWPN/WWNN of the powered-down physical port  204  and perform the tasks that used to be performed by physical port  204 . Preferably, the virtualization process is performed in a way that the host server housing the HBA  102  is not aware of the migration of the physical port  204  to the virtual port  206  and that the operation of the fabric switch  106  is unaffected by the migration. As far as the operating system (OS) and applications on the server are concerned, there has been no change in network connectivity to the rest of the network. Nevertheless, because one of the physical ports  204  has been turned off, electrical power that is typically required to run that physical port  204  is no longer needed. Even though the remaining physical port  202 , hosting the virtual port  206 , is now responsible for handling all connectivity of the HBA  102 , it does not require additional power to run. As such, the total amount of power consumed by the HBA  102  maybe reduced as a result of this port migration process. 
         [0021]      FIG. 3  illustrates exemplary steps of a method of port migration of a first physical port to a second physical port. Referring to  FIG. 3 , the first task is to ensure that the first and second ports are connected to the same fabric switch (step  301 ). This can be done by verifying the Fibre Channel fabric ID of the fabric switch. Next, all input/output traffic through the first port (i.e., the physical port to be migrated) is paused (step  302 ). The duration of the pause is ideally very short (e.g., about a second). After the traffic is cleared, the link between the first port and the fabric switch can be dropped (step  303 ). In other embodiments, other actions to reduce the power consumption of the first port may be additionally or alternatively performed. 
         [0022]    As previously mentioned, to keep the connectivity of the host server intact, a virtual port must be created on the second port to replace the powered-down first port. The connectivity of the virtual port should be verified so that the host server can function seamlessly during and after the port migration process. Without the virtual port being ready to take over the connections from the first port, applications on the host server may encounter serious errors because the host server typically does not tolerate losing connection to remote devices, which may be used to store critical programs and data that the applications on the server need. Preferably, the migrating process should effectively create a transition to the virtual port in such a way that the OS and applications on the host server can function as usual without detecting the transition from the physical port and the virtual port. 
         [0023]    According to this embodiment, the WWPN and WWNN of the first physical port are first noted (step  304 ). Subsequently, an NPIV-based virtual port on the second port is created using the WWPN/WWNN of the first port so that the newly created virtual port can assume the identity of the first port (step  305 ). The virtual port may then be discovered by the host server and log into all the appropriate target storage devices on the network (step  306 ). After the connectivity between the virtual port and the storage devices is reestablished, I/O traffic to the server is resumed and redirected to the virtual port (step  307 ). Because the virtual port has adopted the same WWPN/WWNN as the powered-down first port, the host server would not know that the physical communication channels for some of its communication has been changed, that a virtual port on the second port, instead of the first port, is now being used to connect to target device. As far as the server is concerned, there has been no change in connectivity to the network. As such, the first physical port can be safely shut down without impacting the connectivity of the hosting server. The process can be carried out for other ports on the same HBA or different HBAs of the server. 
         [0024]    Although the migration of one physical port to another physical port is described above, it is to be understood that multiple ports can be migrated to a single second port in the same way as long as the second port has enough bandwidth for network traffic. If all physical ports of one HBA are migrated to one or more physical ports on another HBA, the first HBA can be shut off completely. The more physical ports that can be virtualized on the second port, the more power can be saved by shutting down these physical ports. 
         [0025]    In another embodiment, the port to be migrated can itself be a virtual port. The same virtualization technique can be used to migrate one or more virtual ports on a first physical device (e.g., a first physical port) to a port of a second physical device. After all of the virtual ports of the first physical device are migrated to the second device, the first physical device can be shut off to save power. 
         [0026]    As such, according to embodiments of the invention, a tradeoff may be made between the aggregated bandwidth of the host server and the amount of power that can be saved. The virtualization process discussed in the embodiments can be performed seamlessly, without any significant interruptions to the operation of the host server. In addition, if the host server shuts down one of more of its physical ports, the corresponding ports on the fabric switch can be optionally turned off. That may reduce the power consumption by the fabric switch. 
         [0027]    The existence of the virtual port on the second port allows the first physical port to be shut down as long as there is sufficient network bandwidth to handle communication from and to the server. Whenever the demand for bandwidth increases, the virtual port on the second port can be shut down and first port can be restarted to provide additional bandwidth. Basically, the above-described virtualization process in  FIG. 3  can be reversed. Similarly, if the second port encounters an error and has to be shut down, the virtual port can be terminated and the first port can be powered up again to serve as a backup to the second port. According to embodiments of the invention, whenever a physical port is reactivated, the corresponding virtual port may be shut off. 
         [0028]    In another aspect of the invention, different methods can be used to determine when to initiate the above-described port migration process to reduce power consumption. In one embodiment, a time-based algorithm is used where the migration of ports is scheduled at a predetermined time, for example, at midnight when usage of the servers on the network is typically at its lowest level. Knowing that the access rate for I/O operations is much less at that time of the day, the servers may automatically switch the network adapters to a low-power mode by shutting off one or more physical ports on one or more the adapters of the servers using virtualization techniques as described above. 
         [0029]    In another embodiment, the servers may be running in a power saving mode (i.e., using virtual ports for network connections) unless there is a need to initiate failover procedures in response to problems with the active adapter or physical port on which the virtual ports are created. Typical high-availability systems may include multiple hardware components (e.g., HBAs) and network paths that are redundant. That is, some of the network adapters or ports serve as backups to other adapters/ports.  FIG. 4  illustrates an example of a redundant system. The redundant system includes four network ports A-D  400 ,  402 ,  404 ,  406 , two fabric switches  408 ,  410 , and a storage device  412 . The network ports  400 ,  402 ,  404 ,  406  may be a part of one or more HBAs or other types of network cards. Two of the ports (A and C)  400 ,  404  are active I/O ports connected to the storage device  412  through fabric switch  408 . Ports B and D  402 ,  406  are failover ports for ports A and C  400 ,  404 , respectively. Both ports B and D  402 ,  406  are connected to the storage device  412  through a second switch  410 , which serves as a backup to switch  408 . 
         [0030]    As illustrated in  FIG. 4 , the redundant network ports  400 ,  402 ,  404 ,  406  and fabric switches  408 ,  410  are designed to provide multiple paths to the storage device  412 . For example, if port A  400  fails, its backup port B  402  may be activated and connection to the storage device  412  may be re-established through port B  402 . Similarly, if the connection between active port C  404  and the storage device  412  is interrupted, port D  406 , the backup port for port C  404 , may be powered up and used to access the remote storage device  412 . 
         [0031]    To save power in this type of redundancy setup, one of the failover ports B and D  402 ,  406  may be shut down and a virtual port  414  may be created on the remaining failover port (e.g., port B). This virtualization process of the port can be carried out according to the exemplary embodiments described above. The virtual port  414  has the connectivity and assumes the identity of the turned-off port D  406 , and can still serve as a backup port to port C  404 . In this example, port B  402  is essentially the only active backup port for both ports A and C  400 ,  404  during normal operation. However, at the command of a failover application, the powered-down physical port D  406  could be re-established to support failover to a separate, redundant physical port (e.g., port B). 
         [0032]    In another embodiment, a prediction-based method can be used to schedule port migration. In this embodiment, the use of physical ports can be controlled by an algorithm designed to predict the I/O load based on past system behavior. In particular, if the I/O load was previously relatively low when the system was in a certain state, port migration may be initiated if the same state occurs again. 
         [0033]    Some conventional application-specific integrated circuits (ASICs) may have mechanisms to shut down portions of its circuit to be able to reduce its overall power consumption. In another aspect of the invention, an ASIC having multiple ports and adapted to perform the power-saving port migration process described above is provided. Any ports or other hardware blocks of the ASIC can be shut off to save power. Given the large number of ASICs that can be found in devices of a conventional network, the potential saving in power consumption can be significant if the ASIC can be programmed to perform the disclosed port migration process. 
         [0034]    In another aspect of the invention, further power savings can be achieved by controlling the hardware associated with the switch ports. Using the data path that exists between the physical port and the fabric switch, commands could be transmitted to the fabric switch to instruct it to shut down one or more physical ports connected to the now-powered-down host based ports. Alternatively, the fabric switch can be instructed to switch to a lower power state (i.e., power saving mode) to reduce power consumption. When the time comes to re-establish the physical connection, a similar power up command could be used. 
         [0035]    Various embodiments of the invention can be implemented in software or firmware of the device or a combination of both. For example, if port migration in a particular device is time-based, the timer may be an application running on the server. The application has to communicate to the kernel space where the driver resides. The device driver is another software entity that controls the operation of the hardware (e.g., an HBA) by instructing the firmware residing in the hardware to carry out the requisite steps of the virtualization process. In this embodiment, the application is the entity that makes the decision regarding when to initiate the port migration process. When the scheduled time arrives, the application may issue a command to the driver and, in response, the driver may issue a command to pause I/O operation in the designated hardware (e.g., one or more Fibre Channel ports) and then create the virtual ports on the still active port(s). I/O operation can be resumed after the virtual port(s) is discovered by the host server. The firmware associated with the hardware (e.g., HBA) may be responsible for shutting down physical ports to conserve power used by the adapter. 
         [0036]      FIG. 5  illustrates another embodiment of an HBA according to embodiments of the invention. As illustrated, the HBA  900  includes one or more processors  902 , a network interface  904 , a host bus interface  908 , and computer readable storage media, such as Random Access Memory (RAM)  906  and non-volatile memory  912 . The various components of the HBA  900  are all connected to a bus  914  in the HBA  900  and adapted to communicate with each other using the bus  914 . The RAM  912  and the non-volatile memory  906  may be used to store firmware of the HBA  900  and other data. In other embodiments, the firmware may be stored on an external computer-readable storage medium such as a disk and loaded into the HBA  900  during operation. The host bus interface  908  connects the HBA  700  to its host via a host bus  910 . The network interface  904  provides a gateway to an external network. 
         [0037]      FIG. 6  illustrates an exemplary host device according to an embodiment of the invention. The host device  1000  includes one or more processors  1002 , a storage device  1004 , a network interface  1010 , RAM  1006 , and non-volatile memory  1008 . The host device  1000  may also include one or more device drivers and one or more HBAs (not shown) as described above in view of  FIG. 5 . The processor  1002  may execute instructions stored in computer-readable storage media such as the RAM  1006  and the non-volatile memory  1008 . The storage device  1004  may be a disk capable of storing programs such as firmware for the HBA. The host device is adapted to transmit and receive data from the network using the network interface  1010 . 
         [0038]    Although embodiments of this invention have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of embodiments of this invention as defined by the appended claims.