- The fundamental unit of virtualized client in an IaaS deployment is called a workload.
- A workload simulates the ability of a certain type of real or physical server to do an amount of work.
- The work done can be measured by the number of Transactions Per Minute (TPM) or a similar metric against a certain type of system.
- In addition to throughput, a workload has certain other attributes such as Disk I/Os measured in Input/Output Per Second IOPS, the amount of RAM consumed under load in MB, network throughput and latency, and so forth.
- In a hosted application environment, a client’s application runs on a dedicated server inside a server rack or perhaps as a standalone server in a room full of servers.
- In cloud computing, a provisioned server called an instance is reserved by a customer, and the necessary amount of computing resources needed to achieve that type of physical server is allocated to the client’s needs.
The above figure shows how three virtual private server instances are partitioned in an IaaS stack.
The three workloads require three different sizes of computers: small, medium, and large.
A client would reserve a machine equivalent required to run each of these workloads.
The IaaS infrastructure runs these server instances in the data center that the service offers, drawing from a pool of virtualized machines, RAID storage, and network interface capacity.
These three layers are expressions of physical systems that are partitioned as logical units. LUNs, the cloud interconnect layer, and the virtual application software layer are logical constructs.
LUNs are logical storage containers, the cloud interconnect layer is a virtual network layer that is assigned IP addresses from the IaaS network pool, and the virtual application software layer contains software that runs on the physical VM instance(s) that have been partitioned from physical assets on the IaaS’ private cloud.
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