local-lvm.adoc

   1 Logical Volume Manager (LVM)
   2 ----------------------------
   3 ifdef::wiki[]
   4 :pve-toplevel:
   5 endif::wiki[]
   6
   7 Most people install {pve} directly on a local disk. The {pve}
   8 installation CD offers several options for local disk management, and
   9 the current default setup uses LVM. The installer let you select a
  10 single disk for such setup, and uses that disk as physical volume for
  11 the **V**olume **G**roup (VG) `pve`. The following output is from a
  12 test installation using a small 8GB disk:
  13
  14 ----
  15 # pvs
  16   PV         VG   Fmt  Attr PSize PFree
  17   /dev/sda3  pve  lvm2 a--  7.87g 876.00m
  18
  19 # vgs
  20   VG   #PV #LV #SN Attr   VSize VFree
  21   pve    1   3   0 wz--n- 7.87g 876.00m
  22 ----
  23
  24 The installer allocates three **L**ogical **V**olumes (LV) inside this
  25 VG:
  26
  27 ----
  28 # lvs
  29   LV   VG   Attr       LSize   Pool Origin Data%  Meta%
  30   data pve  twi-a-tz--   4.38g             0.00   0.63
  31   root pve  -wi-ao----   1.75g
  32   swap pve  -wi-ao---- 896.00m
  33 ----
  34
  35 root:: Formatted as `ext4`, and contains the operation system.
  36
  37 swap:: Swap partition
  38
  39 data:: This volume uses LVM-thin, and is used to store VM
  40 images. LVM-thin is preferable for this task, because it offers
  41 efficient support for snapshots and clones.
  42
  43 For {pve} versions up to 4.1, the installer creates a standard logical
  44 volume called ``data'', which is mounted at `/var/lib/vz`.
  45
  46 Starting from version 4.2, the logical volume ``data'' is a LVM-thin pool,
  47 used to store block based guest images, and `/var/lib/vz` is simply a
  48 directory on the root file system.
  49
  50 Hardware
  51 ~~~~~~~~
  52
  53 We highly recommend to use a hardware RAID controller (with BBU) for
  54 such setups. This increases performance, provides redundancy, and make
  55 disk replacements easier (hot-pluggable).
  56
  57 LVM itself does not need any special hardware, and memory requirements
  58 are very low.
  59
  60
  61 Bootloader
  62 ~~~~~~~~~~
  63
  64 We install two boot loaders by default. The first partition contains
  65 the standard GRUB boot loader. The second partition is an **E**FI **S**ystem
  66 **P**artition (ESP), which makes it possible to boot on EFI systems.
  67
  68
  69 Creating a Volume Group
  70 ~~~~~~~~~~~~~~~~~~~~~~~
  71
  72 Let's assume we have an empty disk `/dev/sdb`, onto which we want to
  73 create a volume group named ``vmdata''.
  74
  75 CAUTION: Please note that the following commands will destroy all
  76 existing data on `/dev/sdb`.
  77
  78 First create a partition.
  79
  80  # sgdisk -N 1 /dev/sdb
  81
  82
  83 Create a **P**hysical **V**olume (PV) without confirmation and 250K
  84 metadatasize.
  85
  86  # pvcreate --metadatasize 250k -y -ff /dev/sdb1
  87
  88
  89 Create a volume group named ``vmdata'' on `/dev/sdb1`
  90
  91  # vgcreate vmdata /dev/sdb1
  92
  93
  94 Creating an extra LV for `/var/lib/vz`
  95 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  96
  97 This can be easily done by creating a new thin LV.
  98
  99  # lvcreate -n <Name> -V <Size[M,G,T]> <VG>/<LVThin_pool>
 100
 101 A real world example:
 102
 103  # lvcreate -n vz -V 10G pve/data
 104
 105 Now a filesystem must be created on the LV.
 106
 107  # mkfs.ext4 /dev/data/vz
 108
 109 At last this has to be mounted.
 110
 111 WARNING: be sure that `/var/lib/vz` is empty. On a default
 112 installation it's not.
 113
 114 To make it always accessible add the following line in `/etc/fstab`.
 115
 116  # echo '/dev/pve/vz /var/lib/vz ext4 defaults 0 2' >> /etc/fstab
 117
 118
 119 Resizing the thin pool
 120 ~~~~~~~~~~~~~~~~~~~~~~
 121
 122 Resize the LV and the metadata pool can be achieved with the following
 123 command.
 124
 125  # lvresize --size +<size[\M,G,T]> --poolmetadatasize +<size[\M,G]> <VG>/<LVThin_pool>
 126
 127 NOTE: When extending the data pool, the metadata pool must also be
 128 extended.
 129
 130
 131 Create a LVM-thin pool
 132 ~~~~~~~~~~~~~~~~~~~~~~
 133
 134 A thin pool has to be created on top of a volume group.
 135 How to create a volume group see Section LVM.
 136
 137  # lvcreate -L 80G -T -n vmstore vmdata