Re: [linux-lvm] LVM performance vs direct dm-thin

[Zdenek Kabelac <zdenek.kabelac@gmail.com>]

Dne 29. 01. 22 v 21:34 Demi Marie Obenour napsal(a):
> How much slower are operations on an LVM2 thin pool compared to manually
> managing a dm-thin target via ioctls?  I am mostly concerned about
> volume snapshot, creation, and destruction.  Data integrity is very
> important, so taking shortcuts that risk data loss is out of the
> question.  However, the application may have some additional information
> that LVM2 does not have.  For instance, it may know that the volume that
> it is snapshotting is not in use, or that a certain volume it is
> creating will never be used after power-off.
> 

Hi

Short answer: it depends ;)

Longer story:
If you want to create few thins per hour - than it doesn't really matter.
If you want to create few thins in a second - than the cost of lvm2 management 
is very high  - as lvm2 does far more work then just sending a simple ioctl 
(as it's called logical volume management for a reason)

So brave developers may always write their own management tools for their 
constrained environment requirements that will by significantly faster in 
terms of how many thins you could create per minute (btw you will need to also 
consider dropping usage of udev on such system)

It's worth to mention - the more bullet-proof you will want to make your 
project - the more closer to the extra processing made by lvm2 you will get.

However before you will step into these waters - you should probably evaluate 
whether thin-pool actually meet your needs if you have that high expectation 
for number of supported volumes - so you will not end up with hyper fast 
snapshot creation while the actual usage then is not meeting your needs...

Regards

Zdenek

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