[linux-lvm] Discussion: performance issue on event activation mode

[Martin Wilck]

On Thu, 2021-09-30 at 16:07 +0800, heming.zhao at suse.com wrote:
> On 9/30/21 3:51 PM, Martin Wilck wrote:
> 
> 
> Another performance story:
> The legacy lvm2 (2.02.xx) with lvmetad daemon, the event-activation
> mode
> is very likely timeout on a large scale PVs.
> When customer met this issue, we suggested them to disable lvmetad.
> 

Right. IIRC, that used to be a common suggestion to make without having
detailed clues about the issue at hand... it would help more often than
not.

In theory, I believe that a well written daemon maintaining and
consistent internal state (and possibly manipulating it) would scale
better than thousands of clients trying to access state in some shared
fashion (database, filesystem tree, whatever). I have no clue why that
didn't work with lvmetad. It had other issues I never clearly
understood, either. No need to discuss it further, as it has been
abandoned anyway.

Martin