[linux-lvm] lvm limitations

[Zdenek Kabelac]

Dne 16. 09. 20 v 0:26 Gionatan Danti napsal(a):
> Il 2020-09-15 23:47 Zdenek Kabelac ha scritto:
>> Speaking of thin volumes - there can be at most 2^24 thin devices
>> (this is hard limit you've ask for ;)) - but you have only  ~16GiB of
>> metadata to store all of them - which gives you ~1KiB of data per such
>> volume -
>> quite frankly this is not too much  - unless as said - your volumes
>> are not changed at all - but then why you would be building all this...
>>
>> That all said -  if you really need that intensive amount of snapshoting,
>> lvm2 is likely not for you - and you will need to build something on your own,
>> as you will need way more efficient and 'targeted' solution for your purpose.
> 
> Thinvols are not activated by default - this means it should be not a big 
> problem managing some hundreds of them, as the OP ask. Or am I missing something?

Hundreds should be 'fine' - but hundred thousands does mean the lvm2 metadata 
will reach GiB range - and this is definitely NOT fine ;)  - since you would 
probably need around way more RAM to even manages this ;) and I'm not talking
about some places with O^2 complexity in the lvm2 code...

The metadata format is simply not going to fly here...

Zdenek