KVM Host Disk Layout
This disk layout has several layers. It uses btrfs, on top of LVM, on top of luks encryption, on top of raid, on top of the disk partitions.
Hardware
Two 16G SSD disks are used for the KVM Host. Four 6T SATA disks are used for the KVM Guests filesystem images.
Mark your disks! Spend time finding your disks S/N. Put a physical sticker on the disk. In the future this will help you identify a failing disk.
KVM Host Disks
Physical Disks and Partitions
sda 16G sda1 512M sda2 512M sda3 15360M sdb 16G sdb1 512M sdb2 512M sdb3 15360M
Raid
md0 raid1 (sda1, sdb1) md1 raid1 (sda3, sdb3)
Luks
md1 luks (md1_crypt)
LVM
md1_crypt lvm (vg_system)
LVM Volumes
Initially the swap partition was 256MM, but it ran full and was increased to 1G. That ran full as well, so a swap partition on the second volume was added too. It seems the KVM host happily swaps and will use many gigabytes of swap if the swap partition is there. The consequence is that the guests are slower to respond. So I recommend only swapping if you are really running out of memory.
vg_system root 4G (/dev/vg_system/root) vg_system swap 256M (/dev/vg_system/swap)
Filesystems and Mountpoints
I use btrfs myself, and have chosen this for its stability, but any modern filesystem should be sufficient.
/dev/vg_system/root / (btrfs) /dev/md0 /boot (btrfs) /dev/vg_system/swap (swap)
KVM Host Disks for Guest Filesystem Images
Physical Disks and Partitions
kvm01:
sdc 3T sdc1 2792G ...
kvm02:
sdc 6T sdc1 5588G sdd 6T sdd1 5588G sde 6T sde1 5588G sdf 6T sdf1 5588G
Raid
md2 raid10 (sdc1, sdd1, sde1, sdf1)
Luks
md2 luks (md2_crypt)
LVM
md2_crypt lvm (vg_storage)
LVM Volumes
vg_storage media 4G (/dev/vg_storage/media)
Filesystems and Mountpoints
/dev/vg_storage/media /mnt/media (btrfs)