Ubuntu 16.04, LVM, Thin Provisioning (thinpool)

Oct 13, 2018 2 min read

Introduction

I've been working on building out my virtual host servers, and figuring out how to configure them to allow building a Kubernetes (k8s) cluster, as well as using LXD containers for some VMs (instead of xen/kvm).

Server stats

I'm running a cluster of host servers. I've always run RAID10 (mirrored pairs, then striped).

  • 3x Dell PowerEdge R610
  • 64GB RAM
  • Six-drive RAID10 (hardware), 120GB SSDs
  • Dual Intel Xeon X5650 @ 2.67GHz (24 cores)
  • /dev/sda partitioned into 40G OS, 4G swap, the remainder (292GB) as LVM (/dev/sda5)

Configure Physical Volume

All three servers are configured/partitioned identically, with the LVM partition as /dev/sda5. Because I setup the LVM partition during installation of Ubuntu 16.04, I am skipping the fdisk/gpart steps to create an LVM partition.

The first thing we need to do is create the physical volume specifying the LVM partition.

pvcreate /dev/sda5

Create Volume Group

Next up, add the physical volume /dev/sda5 to a new volume group vg1.

Disclaimer: the following information may be incorrect, but I'm fairly confident my understanding is correct.

Using the vgcreate command, we'll create a new volume group named vg1 using the physical volume /dev/sda5, and we are passing 64M as the physical extend size.

My understanding of the -s 64M is that this specifies the size to allocate to the logical volumes created within this volume create every time it needs to expand the size. Considering I am creating a few LXD containers as servers, I am saying to allocate 64M at a time. If I had tons of small partitions I think I would probably keep the 4M default.

vgcreate -s 64M vg1 /dev/sda5

Create thinpool

Now that we have a volume group vg1 created, we can create a thinpool, which will be used to create thin-provisioned logical volumes.

I am specifying a size of --size 292G because my volume group is 292.75G.

Honestly I'm not sure what --chunksize 1M does exactly, I came across it in another google page. The default is 64k.

lvcreate --type thin-pool --size 292G --chunksize 1M --thinpool tp1 vg1

Validating physical volume, volume group, and thin pool

Check the physical volume

root@s6:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda5
  VG Name               vg1
  PV Size               292.77 GiB / not usable 20.00 MiB
  Allocatable           yes (but full)
  PE Size               128.00 MiB
  Total PE              2342
  Free PE               0
  Allocated PE          2342
  PV UUID               FqSgcb-qqX0-TaMb-WDFp-FQDn-vm6V-lXtHTf

Check the volume groups, which should only include the newly created vg1.

root@s6:~# vgdisplay
  --- Volume group ---
  VG Name               vg1
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               292.75 GiB
  PE Size               128.00 MiB
  Total PE              2342
  Alloc PE / Size       2342 / 292.75 GiB
  Free  PE / Size       0 / 0
  VG UUID               0Iqkkc-pTA6-pBkt-zGwB-zTYC-VWLW-napw0f

Check the logical volumes, which should only include the newly created thin pool tp1.

root@s6:~# lvdisplay
  --- Logical volume ---
  LV Name                tp1
  VG Name                vg1
  LV UUID                E69O7g-wzvP-6Nxx-49lp-IZK9-IbqK-wOINQJ
  LV Write Access        read/write
  LV Creation host, time s6, 2017-06-03 14:03:34 -0700
  LV Pool metadata       tp1_tmeta
  LV Pool data           tp1_tdata
  LV Status              available
  # open                 0
  LV Size                292.50 GiB
  Allocated pool data    0.00%
  Allocated metadata     0.09%
  Current LE             2340
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:2

Create thin-provisioned volume

lvcreate --thinpool vg1/tp1 --name volume1 --virtualsize 1G

Now check the logical volumes with lvs

root@s6:~# lvs
  LV      VG   Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  tp1     vg1  twi-aotz-- 292.00g             0.00   0.18
  volume1 vg1  Vwi-a-tz--   1.00g tp1         0.00

We now have a thin-provisioned logical volume volume1.

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