Virtualizace

Tomas Krajca, xkrajca@fi.muni.cz

Obsah

Motivation
Types of virtualization
Virtual managers
Virtual hard drives
Demo (Qemu/RHEL)
References

VM ~ hypervisor(host, guest₁...guest_n)
Guest_n ~ VHDDs + VNICs + VPrinters + VCPUs + VRAM + ... + VT

Motivation

Benefits

Virtual HW never gets old (out of warranty)
Migration
Resource utilization/energy consumption
Scalability/availability
Disaster recovery scenarios

Shortcomings

Complexity/special knowledge of V technologies
Propagation of a single physical HW failure

Types of virtualization

Containers/OS-level virtualization
- Multiple isolated user-space instances in one OS - resource/impact limitation for each user
- Virtual hosting environments, Applications isolation
- +Little overhead, -not as flexible
- Chroot, BSD jail, VServer, OpenVZ/Virtuozzo, ...
HW emulation
- Emulates specific type of HW for guests (i386, x86_64, mips, ...)
- Dynamic binary translation, precompiled
- +Simple/fast, -not as flexible
- QEMU (qemu-system-x86_64, qemu-system-mips, ...)
- Server/desktop virtualization/isolation, HW drivers testing/development
Paravirtualization
- SW interface of the underlying HW to VMs
- +Certain tasks can be executed directly on HW, -Guest OS has to be ported
- e.g. XEN - Domain 0 (VMM) provides SW interface for Domains U
- Server/desktop virtualization/isolation, cloud computing
- User-mode Linux, Lguest, XEN, VMware
Full virtualization
- Complete HW simulation
- +Guest OS does not have be ported (guest OS appears to run on bare HW)
- Server/desktop virtualization/isolation, cloud computing
- KVM, XEN, VMware

Virtual managers

CLI-based - plain qemu/kvm, virsh/libvirt
GUI-based - VMM/virt-manager
Cloud-based - Eucalyptus

Virtual hard drives

vvfat: Virtual VFAT, vpc: Windows Virtual PC
dmg: Macintosh disk image
cloop: Linux compressed loop
vmdk: VMware virtual machine disk format
qcow2?: QEMU Copy-on-write
raw: Raw file system
cow: User-mode Linux copy-on-write
vdi: VirtualBox

Demo (Qemu/RHEL)

        # yum install -y qemu
        # qemu-img create -f raw qemu-hdd.raw 5G 
        Formatting 'qemu-hdd.raw', fmt=raw size=5368709120 
        # qemu-system-i386 -hda ./qemu-hdd.raw -m 512 -net nic -net user -localtime -boot d -cdrom ubuntu-12.04.1-server-i386.iso -vnc :1 # install
        # # net: 10.0.2.0/24, DHCP, VLAN0, GW .2, DNS .3
        # qemu-system-i386 -hda ./qemu-hdd.raw -m 512 -net nic -net user -localtime -vnc :1 # boot
        # # migration ~ copy/move virtual hard drive, launch again
        # cp ./qemu-hdd.raw /backup/qemu-hdd.raw # backup
        # qemu-img info ./qemu-hdd.raw
        image: qemu-hdd.raw
        file format: raw
        virtual size: 5.0G (5368709120 bytes)
        disk size: 387M
        # fdisk -l qemu-hdd.raw 
        Disk qemu-hdd.raw: 5368 MB, 5368709120 bytes
        255 heads, 63 sectors/track, 652 cylinders, total 10485760 sectors
        Units = sectors of 1 * 512 = 512 bytes
        Sector size (logical/physical): 512 bytes / 512 bytes
        I/O size (minimum/optimal): 512 bytes / 512 bytes
        Disk identifier: 0x000427f0

               Device Boot      Start         End      Blocks   Id  System
        qemu-hdd.raw1            2048     9437183     4717568   83  Linux
        qemu-hdd.raw2         9439230    10483711      522241    5  Extended
        qemu-hdd.raw5         9439232    10483711      522240   82  Linux swap / Solaris
        # mount -o loop,offset=$((2048*512)) qemu-hdd.raw tmp/

Virtualizace

Tomas Krajca, xkrajca@fi.muni.cz

Obsah

Motivation

Benefits

Shortcomings

Types of virtualization

Virtual managers

Virtual hard drives

Demo (Qemu/RHEL)

Literatura