Distributed shared memory
Distributed Shared Memory (DSM) is a term used in computer science and refers to the distribution of the main memory of computer clusters . Since the individual CPUs are not located on a common mainboard , there is also no common memory bus over which they could negotiate access to the memory (e.g. using MESI ). Directory-based protocols are therefore typically used.
DSM is an intermediate form of the well-known distributed memory and shared memory architectures. In general, a DSM is understood to mean a virtual shared memory, which means that the user has the view of a shared memory architecture. The actual memory is, however, distributed over different, separate and independent physical memories. A DSM system thus represents a mediation layer between user and hardware.
A distinction is made between the following groups:
- Virtual Shared Memory (VSM), systems with hardware support, i.e. the consistency of the data is partially or completely ensured by hardware mechanisms
- Shared Virtual Memory (SVM), the memory is kept up-to-date without hardware support
- Distributed Shared Memory (DSM), memory management without replication of the data, i.e. there are no copies. This avoids inconsistencies in the main memory (see also NUMA ).
Abstract look at DSM
