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 Logical Volume
  44 called ``data'' which is mounted at `/var/lib/vz`
  45 Starting from 4.2 the Logical Volume ``data'' is a LVM thin volume, used
  46 for block based storage of guest systems, and `/var/lib/vz` is simply a
  47 directory on the root file system.
  48
  49 Hardware
  50 ~~~~~~~~
  51
  52 We highly recommend to use a hardware RAID controller (with BBU) for
  53 such setups. This increases performance, provides redundancy, and make
  54 disk replacements easier (hot-pluggable).
  55
  56 LVM itself does not need any special hardware, and memory requirements
  57 are very low.
  58
  59
  60 Bootloader
  61 ~~~~~~~~~~
  62
  63 We install two boot loaders by default. The first partition contains
  64 the standard GRUB boot loader. The second partition is an **E**FI **S**ystem
  65 **P**artition (ESP), which makes it possible to boot on EFI systems.
  66
  67
  68 Creating a Volume Group
  69 ~~~~~~~~~~~~~~~~~~~~~~~
  70
  71 Let's assume we have an empty disk `/dev/sdb`, onto which we want to
  72 create a Volume Group named ``vmdata''.
  73
  74 First create a partition.
  75
  76  # sgdisk -N 1 /dev/sdb
  77
  78 Create a **P**hysical **V**olumes (PV) without confirmation and 250K
  79 metadatasize.
  80
  81  # pvcreate --metadatasize 250k -y -ff /dev/sdb1
  82
  83 Create a **V**olume **G**roup (VG) named ``vmdata'' on `/dev/sdb1`
  84
  85  # vgcreate vmdata /dev/sdb1
  86
  87
  88 Creating an extra LV for `/var/lib/vz`
  89 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  90
  91 This can be easily done by creating a new thin LV.
  92
  93  # lvcreate -n <Name> -V <Size[M,G,T]> <VG>/<LVThin_pool>
  94
  95 A real world example:
  96
  97  # lvcreate -n vz -V 10G pve/data
  98
  99 Now a filesystem must be created on the LV.
 100
 101  # mkfs.ext4 /dev/data/vz
 102
 103 At last this has to be mounted.
 104
 105 WARNING: be sure that `/var/lib/vz` is empty. On a default installation it's not.
 106
 107 To make it always accessible add the following line in `/etc/fstab`.
 108
 109  # echo '/dev/pve/vz /var/lib/vz ext4 defaults 0 2' >> /etc/fstab
 110
 111
 112 Resizing the thin pool
 113 ~~~~~~~~~~~~~~~~~~~~~~
 114
 115 NOTE: When extending the data pool, the metadata pool must be extended with it.
 116
 117 Resize the LV and the metadata pool can be achieved with the following command.
 118
 119  # lvresize --size +<size[\M,G,T]> --poolmetadatasize +<size[\M,G]> <VG>/<LVThin_pool>
 120
 121
 122 Create a LVM-Thin pool
 123 ~~~~~~~~~~~~~~~~~~~~~~
 124
 125 A thin pool has to be created on top of a volume group.
 126 How to create a Volume Group see Section LVM.
 127
 128  # lvcreate -L 80G -T -n vmstore vmdata