local-lvm.adoc

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