Table of Contents
Overview
A bare-metal is a service that makes it possible to run directly jobs on hardware resources. Think of it as a set of multi-core hosts on which multi-threaded processes can be started using something like Ssh. The service does not perform any space-sharing among the jobs. In other words, jobs submitted to the service execute concurrently in a time-shared manner. It is the responsibility of the job submitter to pick hosts and/or numbers of cores for each task, e.g., to enforce space-sharing of cores. The only resource allocation performed by the service is that it ensures that the RAM capacity of a host is not exceeded. Tasks that have non-zero RAM requirements are queued in FCFS fashion at each host until there is enough RAM to execute them (think of this as each host running an OS that disallows swapping and implements a FCFS access policy for RAM allocation).
Creating a bare-metal compute service
In WRENCH, a bare-metal service represents a compute service (wrench::ComputeService), which is defined by the wrench::BareMetalComputeService class. An instantiation of a bare-metal service requires the following parameters:
- The name of a host on which to start the service (this is the entry point to the service);
- A set of compute hosts in a map (
std::map), where each key is a hostname and each value is a tuple (std::tuple) with a number of cores and a RAM capacity. - A scratch space size, i.e., the size in bytes of storage local to the bare-metal service (used to store workflow files, as needed, during job executions)
- Maps (
std::map) of configurable properties (wrench::BareMetalComputeServiceProperty) and configurable message payloads (wrench::BareMetalComputeServiceMessagePayload).
The example below shows how to create an instance of a bare-metal service that runs on host "Gateway", provides access to 4 cores and 1GiB of RAM on host "Node1" and to 8 cores and 4GiB of RAM on host "Node2", and has a scratch space of 1TiB. Furthermore, the thread startup overhead is configured to be one hundredth of a second:
Bare-metal service properties
In addition to properties inherited from wrench::ComputeServiceProperty, a bare-metal service supports the following properties:
