text: 1. Field of the Invention
  The present invention relates generally to replaceable electronics modules and, more particularly, to automatically maintaining configuration information in replaceable electronic modules.
  2. Related Art
  Advances in miniaturization of computer, communication and other electronic equipment have led to the development of so-called “blade” systems, which permit several circuit boards (“blades”) to be installed in a single chassis. The chassis typically includes components, such as power supplies, cooling fans, a blade manager and other components that are shared by all the blades installed in the chassis. The blades typically plug into a backplane of the chassis, which distributes power and data signals between the blades and blade manager, and other components. This arrangement enables a large number of blades to be housed in a relatively small chassis. Oftentimes, the chassis is dimensioned to be mounted in a rack, such as a server rack with other rack-mounted equipment.
  Blades are typically designed to be “hot swappable”, that is, they can be installed into or removed from a chassis without removing power from all components in the chassis. This enables an operator or system manager to replace a failed or failing blade with a replacement blade without adversely affecting real-time operations of other chassis components. In addition, spare blades can be installed in a chassis, without activating them, to serve as “hot standby” blades.
  Blades can perform various functions. Most blades contain entire computers, including single or multiple processors, memory and network interfaces. Most computer blades are used as servers while others are used as communication devices, such as routers, firewalls or switches. Some blades contain specialized hardware components, in addition to or instead of processors, memory, etc. Typically, any type of blade can be plugged into any slot of a chassis. This enables an operator or system manager to “mix and match” blades in a chassis so that requisite operations can be performed by the blade system. In addition, the mixture of blade types can be changed to accommodate changes in operational requirements.
  Some server blades include disk drives. Other blades access disk drives that are located elsewhere in the chassis or are connected to the chassis by computer network hardware. Logical network connections between these blades and off-blade disk drives can be established by the blade manager. Since these blades can be connected to different disk drives containing different software at different times, these blades can execute different operating systems and/or application programs, and can access different data at different times. For example, a system operator might choose to logically connect a blade to different disk drives to execute different application programs at different times of a day. In another example, if a blade fails, logical connections from off-blade disk drives that were formerly used by the failed blade can be redirected to a replacement or hot standby blade.
  Some blades can be field-upgraded, such as by installing additional memory, processors or other components on the blades. In contrast, some manufacturers prefer to produce blades that are fully populated with such additional hardware. These manufacturers selectively enable or disable the additional hardware when the blades are manufactured, to tailor the blade capabilities to the to customers' initial needs and budgets. Later, if a customer purchases a license to upgrade a blade, all or a portion of the additional hardware can be enabled without reconfiguring (which requires removal of the blade from the chassis) or replacing the blade.
  Typically, blade configuration information is stored in an electrically-erasable programmable read-only memory (EE-PROM) on each blade. This configuration information can include the blade's serial number and other license information, such as the amount of memory and number of processors that are enabled, i.e., permitted to be operational. When such a blade is to be upgraded, a system manager or field service technician updates the license information stored in the EE-PROM. The system manager, technician, or operator (hereinafter “system manager”) typically connects a keyboard, monitor and mouse to the blade or the blade manager and thereby enters the license information.
  Similarly, some software is licensed on a per-blade basis. Such software typically accesses the blade's serial number or other license information in the EE-PROM each time the software begins executing to ascertain if it is being executed by a licensed blade.
  The ease with which failed blades can be replaced, and the ability to logically connect different disk drives to a blade at different times, have made blade systems popular with data centers and information technology (IT) managers. When a replacement blade is installed it must be configured to have similar hardware and software capabilities as the replaced blade to continue operations under the established license.
  For example, if a failed blade is replaced, its replacement blade should have software license information and a hardware configuration (e.g. number of processors, amount of memory, I/O devices, etc.) similar to the failed blade. A system manager must typically enter configuration information into the EE-PROM of the replacement blade Typically such configuration information is the same as or similar to the failed blade's configuration information. Because the serial number of the replacement blade can be changed in its EE-PROM, software that is licensed to be executed by the failed blade can be executed by the replacement blade.
  There are other circumstances in addition to license upgrades and blade replacement in which the configuration information must be changed. For example, when a blade is logically redirected to a different (second) disk drive, the system manager must typically enter configuration information into the EE-PROM of the blade to inform it of the disk drive to use and/or enable hardware and/or licenses required by software that will be executed from the second disk drive.
  To be able to enter appropriate configuration information into blades, a system manager typically records configuration information for each blade of a blade system. However, recording the configuration information for each blade poses problems. Some system managers have resorted to writing configuration information on pieces of tape and adhering the tape pieces to the blades or chassis adjacent to where the blades are installed. However, the high density of blades in a blade system makes this solution less than satisfactory. Furthermore, entering this configuration information through a keyboard and monitor is error prone.