QEMU 1.2.0 improves live migration
Among the new features of version 1.2.0 of QEMU is support for passing through PCI devices to hardware-virtualised Xen guests. The open source system emulator is used in both the KVM and Xen virtualisation platforms, but can also be used independently. The new release can migrate active guest systems to different hosts (live migration) even if the guests use USB storage media and pass-through devices. In addition, live migration is said to be more reliable for guest systems that use large amounts of RAM.
The QEMU Guest Agent (GA) now supports an fstrim command which discards (trims) storage blocks not in use by the filesystem, which is potentially relevant for solid-state drives (SSDs) and storage systems that use thin provisioning. CD drives can now be accessed via AHCI, and qemu-img offers a new check command for repairing Qcow2 and Qed images. A "Lazy Refcount Mode" has been added to improve the write-through performance of the Qcow2 support. The block layer's default caching method is now "writeback"; guest systems can use a new interface to modify the write cache configuration in order to improve performance or reduce the likelihood of data corruption in case of a crash.
QEMU 1.2.0 supports the emulation of three further SCSI host bus adapters, which can be useful when using older operating systems. Also new are the emulation of an OpenRISC system and of the i.MX32 ARM platform. QEMU now supports the LPAE (Large Physical Address Extensions) ARM technology on platforms with Cortex A15 CPUs.
- Version 1.0 of QEMU published, a report from The H.