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Wilmington, North Carolina once had a thriving Black middle class and an elected interracial government. In 1898 white supremacists used violence to overthrow that government, kill Black residents and drive many others from the city.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
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Live migration, also called migration, refers to the process of moving a running virtual machine (VM) between different physical machines in a manner that the VM and applications running within the VM are mostly unaffected. Memory, storage, and network connectivity of the virtual machine are transferred from the original host machine to the destination. The time between stopping the VM or application on the source and resuming it on destination is called "downtime" or "blackout".[1]
Live migration requires the entire VM's state to be transferred from the source host to the target host. This state includes the state of any components of the VM, for example, the register contents of the virtual CPUs (vCPUs). The state of the VM is not stable until the VM is paused. For example, until the vCPUs have been paused, the state in the virtual registers may be changing.
The simplest way to implement live migration is to pause the VM, serialize and send the state to the target host, and resume the VM on the target host. Serializing and sending certain state, like the state of the VM's main memory or locally-attached storage devices, can be slow.
If the entire contents of the VM's main memory must be copied while the VM is paused, the VM will have to remain paused for an extended period of time, depending on the size of the VM's main memory. There are several techniques for reducing blackout for large-memory VMs.
Pre-copy memory migration requires the hypervisor to track which pages the guest is writing to. With this ability, the following strategy is possible:[2]
This is the basic pre-copy strategy. Other optimizations can be applied, like not re-sending pages that will likely be dirtied again quickly.[3]
The guest is usually able to write to memory faster than it can be copied to the target, which means that pre-copy might never converge to a small dirty set. If the hypervisor does not throttle writes to guest memory, blackout time may remain large, even with pre-copy memory migration.
Post-copy memory migration is a strategy for transferring a VM's main memory outside of blackout. It can complement pre-copy by reducing pause time when pre-copy does not converge on a small set of dirty pages.
It requires the hypervisor to intercept guest memory accesses, allowing the VM to resume on the target host without a complete memory copy. Accesses to pages not yet present on the target (e.g., pages dirtied during pre-copy) are fetched on demand by the hypervisor.[4]
To ensure that all dirty pages are eventually transferred, a hypervisor implementing post-copy live migration will also fetch outstanding dirty pages in the background, concurrently with on-demand fetching of dirty pages.
Post-copy transfers each page only once, whereas pre-copy may resend pages multiple times if they are repeatedly modified. However, pre-copy maintains a consistent VM state on the source, while post-copy splits state between source and destination. As a result, failures during post-copy cannot be recovered, unlike pre-copy, which can be restarted.[5]
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
Live migration, also called migration, refers to the process of moving a running virtual machine (VM) between different physical machines in a manner that the VM and applications running within the VM are mostly unaffected. Memory, storage, and network connectivity of the virtual machine are transferred from the original host machine to the destination. The time between stopping the VM or application on the source and resuming it on destination is called "downtime" or "blackout".
In the context of virtualization, where a guest simulation of an entire computer is actually merely a software virtual machine (VM) running on a host computer under a hypervisor, migration (also known as teleportation, also known as live migration) is the process by which a running virtual machine is moved from one physical host to another, with little or no disruption in service.
OpenVZ (Open Virtuozzo) is an operating system-level virtualization technology for Linux. It allows a physical server to run multiple isolated operating system instances, supporting containerization, virtual private servers (VPSs) and virtual environments (VEs). OpenVZ is similar to Solaris Containers and LXC. Unlike full virtualization solutions or hypervisors such as VMware, Xen, or KVM—which can run diverse operating systems—OpenVZ shares the single, customized Linux kernel of the host machine. By eliminating the resource overhead associated with hardware emulation, OpenVZ delivers performance nearly equivalent to that of a physical machine and enables high container density on a single server configuration. Each OpenVZ container functions as a complete, independent system, featuring its own file system, process tree, user permissions (including a dedicated root account), IP address, and network configuration. Additionally, OpenVZ offers flexible, real-time resource management mechanisms (such as CPU and RAM allocation via User Beancounters or vSwap) and supports live migration, allowing a running container to be moved to another server without service interruption. However, a key limitation of OpenVZ is that all containers are restricted to running Linux and must share the same kernel version as the host server.
Proxmox Virtual Environment (Proxmox VE or PVE) is a free and open-source server virtualization platform developed by Proxmox Server Solutions GmbH. It is based on Debian and combines Kernel-based Virtual Machine (KVM) for hardware-assisted virtual machines with LXC for Linux system containers in a single management environment. Management is available through a web interface, command-line tools and a REST API. The platform integrates clustering, high availability, software-defined networking, storage management, backup and restore, a distributed firewall and live migration. Proxmox VE uses a Proxmox-maintained Linux kernel based on the Ubuntu kernel. Builds were limited to x86-64 until August 2026, when Proxmox released Proxmox VE 9.2 for Arm64 as its first officially supported build on a second processor architecture. Proxmox VE is licensed under the GNU Affero General Public License, version 3. The complete feature set can be used without purchasing a commercial subscription; Proxmox sells optional subscriptions that provide access to its enterprise package repository and, depending on the plan, vendor technical support.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.
