Usama Tanoli

Posted on Jan 6

🪣 Thin Provisioning in LVM – Complete Step by Step Tutorial

#linux #beginners #tutorial #devops

🪣 Buckets of Water Example
Imagine you have 3 friends. Each one asks you for a 1-liter bucket of water.
But you only have 2 liters of water.

Instead of saying “no,” you give each friend an empty bucket and say:
👉 “Don’t worry, I’ll fill it only when you actually need it.”

This is thin provisioning.
You promise more than you physically have, but only allocate space when needed.

💾 In Storage Terms
Normal provisioning (thick):
If you create a 1 GB volume, the system immediately reserves 1 GB — even if you only store 10 MB. Wasteful.

Thin provisioning:
If you create a 1 GB thin volume, the system only uses space when you actually write data. If you write 10 MB, it consumes just 10 MB from the pool. Efficient.⚖️ Thin Provisioning vs. Thick Provisioning

Thick provisioning (traditional): Space is fully reserved upfront, whether you use it or not.

Thin provisioning: Space is allocated on demand, saving storage until it’s actually required.

🚀 Step by Step Implementation
We’ll start with a 10 GB disk (/dev/sda), create a 5 GB partition (/dev/sda1), build a thin pool (3 GB), then test how space is consumed.

1️⃣ Add New Disk
We attach a 10 GB disk (/dev/sda).

`
lsblk

`
`
Output:

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
sda 8:0 0 10G 0 disk

2️⃣ Create a Partition
Make a 5 GB partition and set type to Linux LVM (8e).

fdisk /dev/sda

Inside fdisk:

n → new
p → primary
+5G → size
t → change type → 8e
w → write

Sync partition table:

partprobe /dev/sda

Check:

lsblk

Output:

sda 10G
└─sda1 5G

3️⃣ Create PV and VG
Turn partition into a physical volume (PV):

pvcreate /dev/sda1

Create a volume group (VG):

vgcreate thin_vg /dev/sda1

Check:

vgs

Output:

VG #PV #LV #SN Attr VSize VFree
thin_vg 1 0 0 wz--n- 5.00g 5.00g

4️⃣ Create Thin Pool
We’ll make a 3 GB thin pool.

lvcreate -L 3G --thinpool tp_usama_pool thin_vg

Check:

lvs

Output:

LV VG Attr LSize Pool Origin Data% Meta%
tp_usama_pool thin_vg twi-a-tz-- 3.00g 0.00 11.13

5️⃣ Create Thin LVs
Let’s create 3 LVs of 1 GB each.

lvcreate -V 1G --thin -n thin_vol1 thin_vg/tp_usama_pool
lvcreate -V 1G --thin -n thin_vol2 thin_vg/tp_usama_pool
lvcreate -V 1G --thin -n thin_vol3 thin_vg/tp_usama_pool

6️⃣ Format and Mount
Format:

mkfs.ext4 /dev/thin_vg/thin_vol1
mkfs.ext4 /dev/thin_vg/thin_vol2
mkfs.ext4 /dev/thin_vg/thin_vol3

Create mount points:

mkdir -p /mnt/vol1 /mnt/vol2 /mnt/vol3

Mount:

for i in 1 2 3; do
mount /dev/thin_vg/thin_vol$i /mnt/vol$i
done

Check:

df -hT

Output:

/dev/mapper/thin_vg-thin_vol1 ext4 974M 24K 907M 1% /mnt/vol1
/dev/mapper/thin_vg-thin_vol2 ext4 974M 24K 907M 1% /mnt/vol2
/dev/mapper/thin_vg-thin_vol3 ext4 974M 24K 907M 1% /mnt/vol3

7️⃣ Test by Writing Data
Let’s write 500 MB to each LV.

for d in /mnt/vol1 /mnt/vol2 /mnt/vol3; do
dd if=/dev/zero of=$d/testfile.txt bs=1M count=500 status=progress
done

Now check usage:

lvs

Output (Data% increased):

thin_vol1 thin_vg Vwi-aotz-- 1.00g tp_usama_pool 53.61
thin_vol2 thin_vg Vwi-aotz-- 1.00g tp_usama_pool 53.61
thin_vol3 thin_vg Vwi-aotz-- 1.00g tp_usama_pool 53.61
tp_usama_pool thin_vg twi-aotz-- 3.00g 53.61 23.44

8️⃣ Create Another LV – Warning
Now try adding another 1 GB LV:

lvcreate -V 1G --thin -n thin_vol4 thin_vg/tp_usama_pool

Warning:

Sum of all thin volume sizes (4.00 GiB) exceeds the size of thin pool (3.00 GiB)

This is expected – thin provisioning allows it, but be careful.

9️⃣ Try to Extend Thin Pool (Fails)
Check free VG space:

vgs

Output:

thin_vg 1 5 0 wz--n- 5.00g 1.98g

Now try extending by 2G:

lvextend -L +2G /dev/thin_vg/tp_usama_pool

Error:

Insufficient free space

🔟 Add Another Partition and Extend
Let’s add another 5 GB partition (/dev/sda2).

fdisk /dev/sda

n → new → p → 2 → +5G → w

partprobe /dev/sda

Create PV:

pvcreate /dev/sda2

Extend VG:

vgextend thin_vg /dev/sda2

Check:

vgs

Output:

thin_vg 2 5 0 wz--n- 9.99g 6.98g

Now extend thin pool:

lvextend -L +2G /dev/thin_vg/tp_usama_pool

Output:

Size changed from 3.00 GiB → 5.00 GiB

🔍 Monitoring
Check thin pool and LV usage:

lvs

Output

lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert

thin_vol1 thin_vg Vwi-aotz-- 1.00g tp_usama_pool 53.61

thin_vol2 thin_vg Vwi-aotz-- 1.00g tp_usama_pool 53.61

thin_vol3 thin_vg Vwi-aotz-- 1.00g tp_usama_pool 53.61

thin_vol4 thin_vg Vwi-a-tz-- 1.00g tp_usama_pool 0.00

tp_usama_pool thin_vg twi-aotz-- 5.00g 32.17 16.85

Detailed:

lvdisplay thin_vg/tp_usama_pool

lvdisplay thin_vg/tp_usama_pool
--- Logical volume ---
LV Name tp_usama_pool
VG Name thin_vg
LV UUID nURAHU-0hld-xjOF-97cR-1srt-JdRH-YRcCsE
LV Write Access read/write (activated read only)
LV Creation host, time localhost.localdomain, 2025-09-22 22:07:39 +0500
LV Pool metadata tp_usama_pool_tmeta
LV Pool data tp_usama_pool_tdata
LV Status available
# open 0
LV Size 5.00 GiB
Allocated pool data 32.17%
Allocated metadata 16.85%
Current LE 1280
Segments 1
Allocation inherit
Read ahead sectors auto