[linux-lvm] Reserve space for specific thin logical volumes
zkabelac at redhat.com
Mon Sep 11 15:52:31 UTC 2017
Dne 11.9.2017 v 17:31 Eric Ren napsal(a):
> Hi Zdenek,
> On 09/11/2017 09:11 PM, Zdenek Kabelac wrote:
>> So don't expect lvm2 team will be solving this - there are more prio work....
> Sorry for interrupting your discussion. But, I just cannot help to ask:
> It's not the first time I see "there are more prio work". So I'm wondering:
> can upstream
> consider to have these high priority works available on homepage  or trello
> tool ?
> I really hope upstream can do so. Thus,
> 1. Users can expect what changes will likely happen for lvm.
> 2. It helps developer reach agreements on what problems/features should be on
> priority and avoid overlap efforts.
lvm2 is using upstream community BZ located here:
You can check RHBZ easily for all lvm2 bZ
We usually want to have upstream BZ being linked with Community BZ,
but sometimes it's driven through other channel - not ideal - but still easily
> - lvmetad slows down activation much if there are a lot of PVs on system (say
> 256 PVs, it takes >10s to pvscan
> in my testing).
It's should be opposite case - unless something regressed recently...
Easiest is to write out lvm2 test suite some test.
And eventually bisect which commit broke it...
> - pvmove is slow. I know it's not fault of LVM. The time is almost spent in DM
> (the IO dispatch/copy).
Yeah - this is more or less design issue inside kernel - there are
some workarounds - but since primary motivation was not to overload
system - it's been left a sleep a bit - since focus gained 'raid' target
and these pvmove fixes are working with old dm mirror target...
(i.e. try to use bigger region_size for mirror in lvm.conf (over 512K)
and evaluate performance - there is something wrong - but core mirror
developer is busy with raid features ATM....
> - snapshot cannot be used in cluster environment. There is a usecase: user has
> a central backup system
Well, snapshot CANNOT work in cluster.
What you can do is to split snapshot and attach it different volume,
but exclusive assess is simply required - there is no synchronization of
changes like with cmirrord for old mirror....
> If our upstream have a place to put and discuss what the prio works are, I
> think it will encourage me to do
> more contributions - because I'm not 100% sure if it's a real issue and if
You are always welcome to open Community BZ (instead of trello/github/.... )
Provide justification, present patches.
Of course I cannot hide :) RH has some sort of influence which bugs are more
important then the others...
> it's a work that upstream hopes
> to see, every engineer wants their work to be accepted by upstream :) I can
> try to go forward to do meaningful
> work (research, testing...) as far as I can, if you experts can confirm that
> "that's a real problem. Go ahead!".
We do our best....
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