From: Chuck Reeves (creeves_at_windows.microsoft.com)
Date: Mon Mar 01 2004 - 08:15:02 PST
The paper, "Disco: Running Commodity Operating Systems on Scalable
Multiprocessors", was written in 1997, by a number of researchers at
Stanford University. It describes the design and testing of a virtual
machine monitor called Disco. The system was designed to support the
efficient execution of commodity operating systems on multiprocessor
systems. It is designed to provide a bridge to enable larger commondity
operating systems to run effectively on newer or less main-stream
(NUMA,...) multiprocessor systems.
Disco is described as an additional layer of software running between
the hardware and the operating system. It virtualizes all resources on
the machine including memory, CPU and device I/O. Each executing
instance of the operating system is provided it's own virtual
environment (CPU, memory and devices) against which to execute.
Processor Interface: Emulates all instructions of the supported MIPS
processor. Exposes interrupt control and privileged registers as simple
load and stored instructions on special addresses.
Physical Memory: Full abstraction of memory, starting at address zero.
Also, support page migration and replication to improve locality of
memory access in NUMA environments.
I/O Devices: Intercepts all communication to and from I/O devices using
special device drivers to translate and emulate the operation. DMA
support included. Different virtual disks models can be used to support
sharing and persistence. Network interfaces include Ethernet and FDDI.
Has a special network interface that enables the efficient transfer of
large amounts of data between VMs on the same machine. Only read-only
pages are shared between machines.
Measurements:
The measurements do provide "some" indication that a degree of
scalability can be acheived by running multiple VMs on the same machine.
I thought their work in this area was bit weak. The tests were run on
simulators, they were short in duration and required a number of
modifications to the tested operating system. Additionally, their
scaleablity numbers were not that impressive.
I thought the idea of non-persistent disks
Unlike the Denali model, Disco does provide some facilities for
integration between Virtual Machines including:
Chuck Reeves, creeves_at_microsoft.com
Microsoft | Windows | Directory Services
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