The Technology
Although modern systems include multiple components that need to access the disk, existing systems require that all file accesses be delegated to the operating system/hypervisor. This is due to the fact that only the operating system possesses the logical-to-physical mapping of files to disk blocks and existing disk controllers have no notion of access permissions, so any entity that is physically allowed to access the disk may access other entity. As a result, any interaction between a computing entity and the disk must go through a third party, the operating system or hypervisor. This burdens the performance and power consumption. Moreover, in many cases, the data has to be copied from the disk to the CPU memory and only then to the external device.
The novel technology adds a mapping mechanism to the disk controller that enables hardware and software entities in the computer to securely and directly access their files with low latency. The mapping mechanism is composed of mapping tables that enable the disk controller to map a file offset to the physical disk block that stores the data. In addition, a permissions table defines which hardware device or software entity can access the disk and enforces access permissions. Importantly, the mechanism does not dictate whether the mapping tables should be stored on the disk controller or in main memory. Moreover, the mechanism enables the disk controller to facilitate mapping by creating shadow controllers that export individual files. When an entity (device/virtual machine) wishes to read to or write from a file, it can do so directly without operating system intervention.
Advantages
- Low-latency
- Low-power
- High bandwidth access to on-disk data
Applications and Opportunities
- Cloud computing
- High-Performance Computing
- Remote storage
- Direct accelerator-storage communication
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