[linux-lvm] Reserve space for specific thin logical volumes

[Zdenek Kabelac]

Dne 11.9.2017 v 18:55 David Teigland napsal(a):
> On Mon, Sep 11, 2017 at 03:11:06PM +0200, Zdenek Kabelac wrote:
>>> Aye but does design have to be complete failure when condition runs out?
>>
>> YES
> 
> I am not satisfied with the way thin pools fail when space is exhausted,
> and we aim to do better.  Our goal should be that the system behaves at
> least no worse than a file system reaching 100% usage on a normal LV.

We can reach this goal anytime soon - unless we fix all those filesystem....

And there is other metrics - you can make it way more 'safe' for exhausted
space at the prices of massively slowing down a serializing all writes...

I doubt we would find many users that would easily accept massive slowdown of 
their system just because thin-pool can run out of space....

Global anonymous page-cache is really a hard thing for resolving...

But when you start to limit your usage of thin-pool with some constrains,
you can get much better behaving system.

i.e.     using 'ext4' for mounted  'data' LV should be relatively safe...

And again if you see actual kernel crash OOPS - this is of course a real
kernel bug for fixing...

Regards

Zdenek