Memory virtualization
Encyclopedia
In computer science
, memory virtualization decouples volatile random access memory (RAM) resources from individual systems in the data center, and then aggregates those resources into a virtualized memory pool available to any computer in the cluster. The memory pool is accessed by the operating system or applications running on top of the operating system. The distributed memory pool can then be utilized as a high-speed cache, a messaging layer, or a large, shared memory resource for a CPU or a GPU application.
Memory virtualization implementations are distinguished from shared memory
systems. Shared memory systems do not permit abstraction of memory resources, thus requiring implementation with a single operating system instance (i.e. not within a clustered application environment).
Memory virtualization is also different from memory-based storage such as solid-state drive
s (SSDs). They both allow sharing the memory space (i.e. RAM, flash memory) in a cluster, but SSDs use an overly complicated and less efficient interface, identical to the interface of hard disk drives.
architectures and virtual memory
techniques. In both fields, the path of innovation has moved from tightly coupled relationships between logical and physical resources to more flexible, abstracted relationships where physical resources are allocated as needed.
Virtual memory systems abstract between physical RAM and virtual addresses, assigning virtual memory addresses both to physical RAM and to disk-based storage, expanding addressable memory, but at the cost of speed. NUMA
and SMP
architectures optimize memory allocation within multi-processor systems. While these technologies dynamically manage memory within individual computers, memory virtualization manages the aggregated memory of multiple networked computers as a single memory pool.
In tandem with memory management
innovations, a number of virtualization techniques have arisen to make the best use of available hardware resources. Application virtualization
was demonstrated in mainframe systems first. The next wave was storage virtualization
, as servers connected to storage systems such as NAS
or SAN
in addition to, or instead of, on-board hard disk drives. Server virtualization, or Full virtualization
, partitions a single physical server into multiple virtual machine
s, consolidating multiple instances of operating systems onto the same machine for the purpose of efficiency and flexibility. In both storage and server virtualization, the applications are unaware that the resources they are using are virtual rather than physical, so efficiency and flexibility are achieved without application changes. In the same way, memory virtualization allocates the memory of an entire networked cluster of servers among the computers in that cluster.
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
, memory virtualization decouples volatile random access memory (RAM) resources from individual systems in the data center, and then aggregates those resources into a virtualized memory pool available to any computer in the cluster. The memory pool is accessed by the operating system or applications running on top of the operating system. The distributed memory pool can then be utilized as a high-speed cache, a messaging layer, or a large, shared memory resource for a CPU or a GPU application.
Description
Memory virtualization allows networked, and therefore distributed, servers to share a pool of memory to overcome physical memory limitations, a common bottleneck in software performance. With this capability integrated into the network, applications can take advantage of a very large amount of memory to improve overall performance, system utilization, increase memory usage efficiency, and enable new use cases. Software on the memory pool nodes (servers) allows nodes to connect to the memory pool to contribute memory, and store and retrieve data. Management software manages the shared memory, data insertion, eviction and provisioning policies, data assignment to contributing nodes, and handles requests from client nodes. The memory pool may be accessed at the application level or operating system level. At the application level, the pool is accessed through an API or as a networked file system to create a high-speed shared memory cache. At the operating system level, a page cache can utilize the pool as a very large memory resource that is much faster than local or networked storage.Memory virtualization implementations are distinguished from shared memory
Shared memory
In computing, shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies. Depending on context, programs may run on a single processor or on multiple separate processors...
systems. Shared memory systems do not permit abstraction of memory resources, thus requiring implementation with a single operating system instance (i.e. not within a clustered application environment).
Memory virtualization is also different from memory-based storage such as solid-state drive
Solid-state drive
A solid-state drive , sometimes called a solid-state disk or electronic disk, is a data storage device that uses solid-state memory to store persistent data with the intention of providing access in the same manner of a traditional block i/o hard disk drive...
s (SSDs). They both allow sharing the memory space (i.e. RAM, flash memory) in a cluster, but SSDs use an overly complicated and less efficient interface, identical to the interface of hard disk drives.
Benefits
- Improves memory utilization via the sharing of scarce resources
- Increases efficiency and decreases run time for data intensive and I/O bound applications
- Allows applications on multiple servers to share data without replication, decreasing total memory needs
- Lowers latency and provides faster access than other solutions such as SSD, SAN or NAS
Products
- RNA networks Memory Virtualization Platform - A low latency memory pool, implemented as a shared cache and a low latency messaging solution.
- ScaleMP - A platform to combine resources from multiple computers for the purpose of creating a single computing instance.
- Wombat Data Fabric – A memory based messaging fabric for delivery of market data in financial services.
Application level integration
In this case, applications running on connected computers connect to the memory pool directly through an API or the file system.Operating System Level Integration
In this case, the operating system connects to the memory pool, and makes pooled memory available to applications.Background
Memory virtualization technology follows from memory managementMemory management
Memory management is the act of managing computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and freeing it for reuse when no longer needed. This is critical to the computer system.Several...
architectures and virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
techniques. In both fields, the path of innovation has moved from tightly coupled relationships between logical and physical resources to more flexible, abstracted relationships where physical resources are allocated as needed.
Virtual memory systems abstract between physical RAM and virtual addresses, assigning virtual memory addresses both to physical RAM and to disk-based storage, expanding addressable memory, but at the cost of speed. NUMA
Non-Uniform Memory Access
Non-Uniform Memory Access is a computer memory design used in Multiprocessing, where the memory access time depends on the memory location relative to a processor...
and SMP
Symmetric multiprocessing
In computing, symmetric multiprocessing involves a multiprocessor computer hardware architecture where two or more identical processors are connected to a single shared main memory and are controlled by a single OS instance. Most common multiprocessor systems today use an SMP architecture...
architectures optimize memory allocation within multi-processor systems. While these technologies dynamically manage memory within individual computers, memory virtualization manages the aggregated memory of multiple networked computers as a single memory pool.
In tandem with memory management
Memory management
Memory management is the act of managing computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and freeing it for reuse when no longer needed. This is critical to the computer system.Several...
innovations, a number of virtualization techniques have arisen to make the best use of available hardware resources. Application virtualization
Application Virtualization
Application virtualization is an umbrella term that describes software technologies that improve portability, manageability and compatibility of applications by encapsulating them from the underlying operating system on which they are executed. A fully virtualized application is not installed in...
was demonstrated in mainframe systems first. The next wave was storage virtualization
Storage Virtualization
Storage virtualization or storage virtualisation is a concept and term used within computer science. Specifically, storage systems may use virtualization concepts as a tool to enable better functionality and more advanced features within the storage system.Broadly speaking, a 'storage system' is...
, as servers connected to storage systems such as NAS
Nas
Nasir bin Olu Dara Jones, who performs under the name Nas , formerly Nasty Nas, is an American rapper and actor. He is regarded as one of the most important figures in hip hop and one of the most skilled and influential rappers of all-time...
or SAN
Storage area network
A storage area network is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices...
in addition to, or instead of, on-board hard disk drives. Server virtualization, or Full virtualization
Full virtualization
In computer science, full virtualization is a virtualization technique used to provide a certain kind of virtual machine environment, namely, one that is a complete simulation of the underlying hardware...
, partitions a single physical server into multiple virtual machine
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
s, consolidating multiple instances of operating systems onto the same machine for the purpose of efficiency and flexibility. In both storage and server virtualization, the applications are unaware that the resources they are using are virtual rather than physical, so efficiency and flexibility are achieved without application changes. In the same way, memory virtualization allocates the memory of an entire networked cluster of servers among the computers in that cluster.
See also
- Virtual memoryVirtual memoryIn computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
- Traditional memory virtualization on a single computer, typically using the translation lookaside buffer (TLB) to translate between virtual and physical memory addresses- Virtual memory management in Hypervisors - Hypervisors manage the physical memory of one server, dynamically apportioning memory among operating system instances (VMware ESX, Xen Hypervisor)
- Data grid - Enables Java application clustering
- In-memory database - Provides faster and more predictable performance than disk-based databases (Gigaspaces, Gemstone Gemfire)
- I/O virtualizationI/O virtualizationInput/output virtualization is a methodology to simplify management, lower costs and improve performance of servers in enterprise environments...
- Creates virtual network and storage endpoints which allow network and storage data to travel over the same fabrics (XSigo I/O Director) - Storage virtualizationStorage VirtualizationStorage virtualization or storage virtualisation is a concept and term used within computer science. Specifically, storage systems may use virtualization concepts as a tool to enable better functionality and more advanced features within the storage system.Broadly speaking, a 'storage system' is...
- Abstracts logical storage from physical storage (NAS, SAN, File Systems (NFS, cluster FS), Volume Management, RAID) - Virtualization management hardware - Hardware solution to accelerate hypervisors (3Leaf Management Solution)
- RAM diskRAM diskA RAM disk or RAM drive is a block of RAM that a computer's software is treating as if the memory were a disk drive...
- Virtual storage device within a single computer, limited to capacity of local RAM. - memcachedMemcachedIn computing, memcached is a general-purpose distributed memory caching system that was originally developed by Danga Interactive for LiveJournal, but is now used by many other sites. It is often used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the...
- InfiniBandInfiniBandInfiniBand is a switched fabric communications link used in high-performance computing and enterprise data centers. Its features include high throughput, low latency, quality of service and failover, and it is designed to be scalable...
- 10 Gigabit Ethernet10 Gigabit EthernetThe 10 gigabit Ethernet computer networking standard was first published in 2002. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s , ten times faster than gigabit Ethernet.10 gigabit Ethernet defines only full duplex point to point links which are generally connected by...
- Distributed shared memoryDistributed shared memoryDistributed Shared Memory , in Computer Architecture is a form of memory architecture where the memories can be addressed as one address space...
- Remote direct memory accessRemote Direct Memory AccessIn computing, remote direct memory access is a direct memory access from the memory of one computer into that of another without involving either one's operating system...
(RDMA) - Locality of referenceLocality of referenceIn computer science, locality of reference, also known as the principle of locality, is the phenomenon of the same value or related storage locations being frequently accessed. There are two basic types of reference locality. Temporal locality refers to the reuse of specific data and/or resources...