System Architecture Design

pSHIELDSystem Architecture DesignPUThis block also maintains a stable storage for storing checkpoint information from every other block, orfrom the middleware layer. This data is retrieved on request, for system recovery. Stable Storage 9 is amemory whose contents survive system malfunctions. It must resist to external and internal failures, andguarantee atomic reads and writes. It is usually implemented using two memory banks and when data issend to this memory, it is first written in bank1, then internally into bank2 and, only when both operationsare completed, the stable write is considered done. Some error detection codes are also added, i.e. ECC,EOS, Parity algorithms. A stable read consists of checking parity bits and comparing both banks. Onlywhen both banks are corrupted or are different from each other, but both with valid codes, the read fails. Asimpler version could be simply the addition of error detection and correction codes. The control of stablewrites and stable reads may be performed by hardware or software. Depending of the stable storagecontrol, the HSM may consist of hardware, software or both. Every detected error (tolerated or not) shouldbe stored for informing the SHSM. These features are necessary to implement the rollback recoverystrategy.6.1.1.1.5 ReconfigurationThis block is responsible for node reconfiguration. The reconfiguration of the system is made by request,usually from middleware, or may also be requested by the SPD Node Status block, as a selfreconfigurationcapability (e.g., a certain threshold of a block’s health has been reached).Reconfiguration may consist on connecting/disconnecting some devices, or reprogramming the FPGA,either totally or partially.6.1.1.1.6 Security and PrivacyThis block is responsible for providing security and privacy related capabilities, such as Data Encryption,Data Decryption, Generation of Cryptographic Keys, etc.These capabilities may be used both by other modules (such as dependability, for encrypting stablestorage data) or by the middleware layer.6.1.1.1.7 pSHIELD InterfaceThis block provides a proper physical interface to the pSHIELD network. It also provides the necessarydrivers and capabilities to the upper levels.6.1.1.1.8 Power ManagementThe Power Management (PM) module is responsible for managing power supply, such as switching toredundant power sources or checking the level of power consumption.6.1.1.1.9 pSHIELD Node Layer Capabilities and FunctionalitiesA pSHIELD Node must provide to the other layers of the pSHIELD framework a set of Node LayerInnovative SPD Functionalities that comply with the pSHIELD conceptual model.The Node Layer capabilities and functionalities are provided by the hardware, firmware or software, in theform of device drivers or other interfacing modules. The legacy node capabilities are always providedthrough the pSHIELD Node Adapter, in the form of pSHIELD Node Capabilities.This section describes the pSHIELD SPD functionalities and capabilities provided by the pSHIELD NodeLayer.9 “Software-Implemented Stable Storage in Main Memory”, João Carlos Cunha, Dep. Engenharia Informática e de Sistemas,Instituto Superior de Engenharia de Coimbra; Centro de Informática e de Sistemas da Universidade de Coimbra Coimbra, Portugal;João Gabriel Silva, Dep. Engenharia Informática, Universidade de Coimbra, Centro de Informática e de Sistemas da Universidadede Coimbra Coimbra, Portugal IX Brazilian Symposium on Fault-Tolerant Computing (SCTF), Florianópolis/SC, Brazil, March 2001PUD2.3.2Issue 5 Page 70 of 122