Word of the Day: memory ballooning

Word of the Day Daily updates on the latest technology terms | May 28, 2014

memory ballooning Memory ballooning is a memory management technique that allows a physical host to take advantage of unused memory on its guest virtual machines (VMs). When a host OS is short on physical memory, the hypervisor polls balloon drivers installed on the guests to request available memory. The guests respond by using page-reclaiming algorithms to determine which pages are available and can be assigned to the balloon drivers. The process of assigning available pages to the driver is known as inflating the balloon. Releasing available pages is known as deflating the balloon. In a positive sense, memory ballooning allows that the total amount of RAM required by guest virtual machines to exceed the amount of physically available RAM on the host. A problem can occur, however, when a balloon driver inflates to the point where the guest VM no longer has the memory it needs to run processes within the guest. In such a scenario, the guest operating system will start swapping things out to deal with its memory issues. This swap activity can negatively affect performance, depending upon the amount of memory to recoup and/or the quality of the storage IOPS delivered to the VM. Other memory-reclaiming techniques include memory overcommit, memory paging, memory mirroring and transparent page sharing. Quote of the Day "Memory Ballooning is a technique that is only engaged when the host is running low on physical memory. If you have a host with 60 GB of physical memory available and the virtual machines are only allocated a total of 30GB of memory, then you may never need to know what memory ballooning is all about." - Eric Shanks   Fun Fact In a VMware environment, the balloon driver only activates when memory becomes scarce. In a Windows Server environment, the balloon driver allocates RAM to the VM on-demand. Related Terms Related Terms hypervisor memory overcommit memory mirroring memory paging transparent page sharing memory management virtual memory paging IOPS Related Tags Capacity planning for virtualization, Virtual machine provisioning and configuration   Required Reading Virtual memory management techniques: A beginner's guide Learn six virtual memory management techniques for improving memory sharing, preventing shortages and resolving memory overutilization. Optimizing resources with vSphere memory management techniques Learn about VMware's vSphere memory management techniques and how they can help you over-allocate memory in a vSphere environment. Memory methods still differ for Microsoft and VMware Dig deep into the memory management differences that still remain between Microsoft Hyper-V R2 SP1 and VMware ESX server virtualization. Stay In Touch FOLLOW WHATIS.COM     CONTACT US For feedback about any of our definitions or to send us ideas for new definitions, please contact us at: editor@techtarget.com About This E-Newsletter This e-newsletter is published by the TechTarget network. To unsubscribe from Whatis.com, click here. Please note, this will not affect any other subscriptions you have signed up for. TechTarget, Whatis, 275 Grove Street, Newton, MA 02466. Contact: webmaster@techtarget.com Copyright 2013 TechTarget. All rights reserved.