操作环境

Centos 6.5 x86_64

qemu-img-0.12.1.2-2.415.el6.3ceph.x86_64

qemu-kvm-0.12.1.2-2.415.el6.3ceph.x86_64

libvirt-python-0.10.2-29.el6_5.12.x86_64

libvirt-0.10.2-29.el6_5.12.x86_64

libvirt-client-0.10.2-29.el6_5.12.x86_64

操作说明

    kvm对于块设备默认使用virtio-blk模板，后来提出virtio-scsi用来取代virtio-blk，可以提高性能以及可扩张性，在virtio-blk模块下，硬盘设备显示字符为/dev/vd\*，在virtio-scsi木块下，硬盘设备显示为/dev/sd\*，下面为操作步骤。
    创建scsi-controller
<controller type='scsi' model='virtio-scsi'/>
    将scsi-controller设备添加在kvm guest中，此时kvm guset应为关闭状态
virsh attach-device --config demo-linux scsi-controller.xml
    创建硬盘设备
#fallocate -l 20480M /var/lib/libvirt/images/sda.img
  创建硬盘sda的xml文件sda.xml
<disk type='file' device='disk'>
        <device name='qemu' type='raw' cache='none'/>
        <source file='/var/lib/libvirt/images/sdc.img'/>
        <target dev='sdc'/>
</disk>
    添加硬盘设备到kvm guest中
#virsh attach-device --config demo-linux sda.xml
   启动kvm guest ，查看硬盘设备
[root@demo-ceph ~]# fdisk -l /dev/sda
Disk /dev/sda: 21.5 GB, 21474836480 bytes
64 heads, 32 sectors/track, 20480 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
 查看现有scsi设备
[root@demo-ceph ~]# lsscsi 
[1:0:0:0]    cd/dvd  QEMU     QEMU DVD-ROM     0.12  -       
[2:0:0:1]    disk    QEMU     QEMU HARDDISK    0.12  -
 查看pci设备，在最后面可以找到基于virtio-scsi的scsi controller。
[root@demo-ceph ~]# lspci
00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
00:01.2 USB controller: Intel Corporation 82371SB PIIX3 USB [Natoma/Triton II] (rev 01)
00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
00:02.0 VGA compatible controller: Cirrus Logic GD 5446
00:03.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 20)
00:04.0 SCSI storage controller: Red Hat, Inc Virtio block device
00:05.0 SCSI storage controller: Red Hat, Inc Virtio block device
00:06.0 RAM memory: Red Hat, Inc Virtio memory balloon
00:07.0 SCSI storage controller: Red Hat, Inc Virtio block device
00:08.0 SCSI storage controller: Red Hat, Inc Virtio SCSI