LVM2 partition alignment

linux partition performance lvm

7,020

On a recent Linux distribution, the kernel should provide the physical sector size of the device and the partition/lvm/mkfs tools should automatically chose the alignment such that it is compatible with the physical sector size (for best performance).

For example on a Debian system of mine:

# cat /sys/block/sdb/queue/physical_block_size
4096
# cat  /sys/block/sdb/queue/logical_block_size
512

Update: To check for kernel support, you can check if /sys contains the mentioned files, you can call fdisk -l to check if it prints this information (it should), you can check the specification of your hard disk (available by your vendor), you can check the changelog and/or source of LVM tools. Most mkfs commands provide a verbose option to see what block size is used. Last but not least you can just do a simple benchmark - e.g. one without any LVM (e.g. whole disk as device) and repeat it when your LVM setup is in place.

7,020

Grzegorz Wierzowiecki

Updated on September 18, 2022

Comments

Grzegorz Wierzowiecki almost 2 years
How to do the following with Linux tools : LVM partition alignment and alignment of partition on LVM ?

What in case where I want to setup LVM partition (for "pv") and then partitions ?

To be more specifig, I'd like to make following setup:
- sda1 - boot , about 256MB
- sda2 - LVM pv On LVM : swap, root, home etc.
How to setup LVM parition and paritions on LVM to obtain best performance? (Command line linux tools please ;) )

Am I right, that when LVM extents are aligned, created partitions are as well ?

What's the best size of block? : Thanks to @maxschlepzig, we have elegant method of obtaining sector size - for example 4k. Now, questions stays, how to apply this knowledge.
- Admin almost 13 years
  
  Hi, Grzegorzu :) You should have a look at answers to this question.
- Admin almost 13 years
  
  Yes, I've looked at LVM manuals and tutorials, but answers I've managed to found where to me too vague. Could you find there precise answer and could reference precisely to any of those resources ?
- Admin almost 13 years
  
  Unfortunately, I myself know very little about LVM, so I can't judge any of the tutorials.
Grzegorz Wierzowiecki almost 13 years

That's great tip. Thanks. Now question stays : how to apply this knowledge while creating LVM partition and partitions on LVM :). . Best, Greg
psusi almost 13 years

@Grzegorz Wierzowiecki as he said, ( recent versions of ) the tools apply it automatically.
Grzegorz Wierzowiecki almost 13 years

@psusi Can I be sure about it ? Is it the case of tools: 'fdisk' , 'cfdisk', 'pvcreate', 'lvcreate' ? Should I just start partitioning and with them, creating lvms and everything will be aligned ? - please, ensure me. References to tools documentation are welcome.
maxschlepzig almost 13 years

@Grzegorz Wierzowiecki, updated the answer with some comments about checking.
Grzegorz Wierzowiecki almost 13 years

I have Seagate ST2000DL003 while is described as 4k disk, while $ cat /sys/block/sdg/queue/physical_block_size gives 512 - I am afraid it's due to "AF" technology. So I'd like to ensure 4k aligning.