The cloud computing environments rely heavily on virtualization that enables the physical hardware resources to be shared among cloud users by creating virtual machines (VMs). With an overloaded physical machine, the resource requests by virtual machines may not be fulfilled, which results in Service Level Agreement (SLA) violations. Moreover, the high performance servers in cloud data centers consume large amount of energy. The dynamic VM consolidation techniques use live migration of virtual machines to optimize resource utilization and minimize energy consumption. An excessive migration of virtual machines may however deteriorate application performance due to the overhead incurring at runtime. In this paper, we propose a normalization-based VM consolidation (NVMC) strategy that aims at placing virtual machines in an online manner while minimizing energy consumption, SLA violations, and the number of VM migrations. The proposed strategy uses resource parameters for determining over-utilized hosts in a virtualized cloud environment. The comparative capacity of virtual machines and hosts is incorporated for determining over-utilized hosts, while the cumulative available-to-total ratio (CATR) is used to find under-utilized hosts. For migrating virtual machines to appropriate hosts, the VM placement uses a criteria based on normalized resource parameters of hosts and virtual machines. For evaluating the performance of VM consolidation, we have performed experimentation with a large number of virtual machines using traces from the PlanetLab workloads. The results show that the NVMC approach outperforms other well-known approaches by achieving a significant improvement in energy consumption, SLA violations, and number of VM migrations.

云计算环境严重依赖虚拟化，通过创建虚拟机 (VM) 使物理硬件资源能够在云用户之间共享。对于过载的物理机，可能无法满足虚拟机的资源请求，从而导致违反服务级别协议 (SLA)。此外，云数据中心的高性能服务器消耗大量能源。动态 VM 整合技术使用虚拟机的实时迁移来优化资源利用率并最大限度地降低能耗。然而，由于运行时产生的开销，虚拟机的过度迁移可能会降低应用程序的性能。在本文中，我们提出了一种基于规范化的 VM 整合 (NVMC) 策略，旨在以在线方式放置虚拟机，同时最大限度地减少能耗、SLA 违规和 VM 迁移次数。所提出的策略使用资源参数来确定虚拟化云环境中过度使用的主机。虚拟机和主机的比较容量用于确定过度使用的主机，而累积可用总比率 (CATR) 用于查找未充分利用的主机。为了将虚拟机迁移到适当的主机，VM 放置使用基于主机和虚拟机的标准化资源参数的标准。为了评估 VM 整合的性能，我们使用来自 PlanetLab 工作负载的跟踪对大量虚拟机进行了实验。