☰

虚拟机的块设备问题

tag-icon • tag-icon qemu block-device libvirt
虚拟机的块设备问题

我的主机中有两个块设备，我试图将它们传递给虚拟机来宾。一个可以完美地工作，而另一个则不能。唯一的区别是，一个是内部驱动器上的逻辑卷，而另一个是基于外部 Thunderbolt 驱动器构建的软件 RAID 上的逻辑卷。我很好奇是否需要做得更好，以确保分区表位于主机和来宾需要的位置。

来宾和主机都运行最新的 Arch Linux。主机中的第一个设备位于 LVM 卷组上的逻辑卷上，/dev/nvme0n1p3该卷组上直接连接到 Intel NUC13 主板

# fdisk -l /dev/HomeServerNUC13VM/HomeServerNUC13Storage 
Disk /dev/HomeServerNUC13VM/HomeServerNUC13Storage: 16 GiB, 17179869184 bytes, 33554432 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
Disklabel type: gpt
Disk identifier: CAEF53EA-821B-4A57-9FFB-E62CE5174E16

Device                                           Start      End  Sectors Size Type
/dev/HomeServerNUC13VM/HomeServerNUC13Storage1    2048  2099199  2097152   1G EFI System
/dev/HomeServerNUC13VM/HomeServerNUC13Storage2 2099200 33552383 31453184  15G Linux filesystem

第二个是不同 LVM 卷组上的逻辑卷，/dev/md127p1其上有一个软件 RAID 5 阵列/dev/nvme{1,2,3,4}n1p1。所有这些物理驱动器都位于外壳中并通过 Thunderbolt 连接到 NUC

# fdisk -l /dev/HomeStorageOWC/HomeServerNUC13Storage 
Disk /dev/HomeStorageOWC/HomeServerNUC13Storage: 2 TiB, 2199023255552 bytes, 536870912 sectors
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 262144 bytes / 786432 bytes
Disklabel type: gpt
Disk identifier: DBF9C573-63AF-417B-ADE6-F6560D0702D9

Device                                      Start       End   Sectors Size Type
/dev/HomeStorageOWC/HomeServerNUC13Storage1   256 536870655 536870400   2T Linux filesystem

我可以访问主机中两个块设备上的分区并kpartx -a毫无问题地安装它们。当我将设备传递给虚拟机来宾时，问题就出现了

   <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native' discard='unmap'/>
      <source dev='/dev/HomeServerNUC13VM/HomeServerNUC13Storage'/>
      <target dev='sda' bus='sata'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native' discard='unmap'/>
      <source dev='/dev/HomeStorageOWC/HomeServerNUC13Storage'/>
      <target dev='sdb' bus='sata'/>
      <address type='drive' controller='0' bus='0' target='0' unit='1'/>
    </disk>

在来宾中/dev/HomeServerNUC13VM显示为/dev/sda并且工作正常，而在/dev/HomeStorageOWC/HomeServerNUC13Storage显示时则显示为/dev/sdb搞砸了。请注意，Disklabel type是dos

# fdisk -l /dev/sdb
GPT PMBR size mismatch (536870911 != 4294967295) will be corrected by write.
Disk /dev/sdb: 2 TiB, 2199023255552 bytes, 4294967296 sectors
Disk model: QEMU HARDDISK   
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Device     Boot Start        End    Sectors Size Id Type
/dev/sdb1           1 4294967295 4294967295   2T ee GPT

如果我在来宾中重新创建分区表和分区，那么来宾中的一切都很好

# fdisk -l /dev/sdb
Disk /dev/sdb: 2 TiB, 2199023255552 bytes, 4294967296 sectors
Disk model: QEMU HARDDISK   
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 00B06790-6D3B-4694-B435-6E9E6E9E12CB

Device     Start        End    Sectors Size Type
/dev/sdb1   2048 4294965247 4294963200   2T Linux filesystem

但回到主机后事情就搞砸了。再次Disklabel type是dos。

# fdisk -l /dev/HomeStorageOWC/HomeServerNUC13Storage 
Disk /dev/HomeStorageOWC/HomeServerNUC13Storage: 2 TiB, 2199023255552 bytes, 536870912 sectors
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 262144 bytes / 786432 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Device                                      Boot Start        End    Sectors Size Id Type
/dev/HomeStorageOWC/HomeServerNUC13Storage1          1 4294967295 4294967295  16T ee GPT

Partition 1 does not start on physical sector boundary.

我删除了 RAID 5 并直接重新创建它，/dev/nvme{1,2,3,4}n1同时直接放置 LVM /dev/md127（即没有分区），然后将 LV 设为 256 GB，但仍然遇到相同的问题。

答案1

答案就在libvirt 文档，特别是在该行中：

blockio logical_block_size='512' physical_block_size='4096'
discard_granularity='4096'

QEMU 也有一个选项；就像是：

-设备 scsi-hd，总线=scsi1.0，驱动器=drive-virtio-disk1，id=virtio-scsi-pci1，物理块大小=4096，逻辑块大小=512

答案2

/dev/nvme0n1我错过的是主机中的内容

Sector size (logical/physical): 512 bytes / 512 bytes

而/dev/nvme{1,2,3,4}n1在主机中有

Sector size (logical/physical): 4096 bytes / 4096 bytes

在来宾中，有问题的设备显示为

Sector size (logical/physical): 512 bytes / 512 bytes

我认为扇区大小的这种不匹配会搞砸分区表。您似乎无法设置虚拟SATA设备的扇区大小，但可以使用virtio设备的blockio参数

<disk type='block' device='disk'>
  <driver name='qemu' type='raw' cache='none' io='native' discard='unmap'/>
  <source dev='/dev/HomeStorageOWC/HomeServerNUC13Web'/>
  <target dev='vda' bus='virtio'/>
  <blockio logical_block_size='4096' physical_block_size='4096'/>
  <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
</disk>

相关内容