[linux-lvm] Possible bug in thin metadata size with Linux MDRAID

Gionatan Danti g.danti at assyoma.it
Mon Mar 20 11:52:07 UTC 2017

On 20/03/2017 12:01, Zdenek Kabelac wrote:
> As said - please try with HEAD - and report back if you still see a
> problem.
> There were couple issue fixed along this path.

Ok, I tried now with tools and library from git:

LVM version:     2.02.169(2)-git (2016-11-30)
Library version: 1.02.138-git (2016-11-30)
Driver version:  4.34.0

I can confirm that now thin chunk size is no more bound (by default) by 
MD RAID chunk. For example, having created a ~500 GB MD RAID 10 array 
with 64 KB chunks, creating a thinpool shows that:

[root at blackhole ~]# lvcreate --thinpool vg_kvm/thinpool -L 500G
[root at blackhole ~]# lvs -a -o +chunk_size
   WARNING: Failed to connect to lvmetad. Falling back to device scanning.
   LV               VG        Attr       LSize   Pool Origin Data% 
Meta%  Move Log Cpy%Sync Convert Chunk
   [lvol0_pmspare]  vg_kvm    ewi------- 128.00m 
   thinpool         vg_kvm    twi-a-tz-- 500.00g             0.00   0.42 
   [thinpool_tdata] vg_kvm    Twi-ao---- 500.00g 
   [thinpool_tmeta] vg_kvm    ewi-ao---- 128.00m 
   root             vg_system -wi-ao----  50.00g 
   swap             vg_system -wi-a-----   7.62g

Should I open a bug against the RHEL-provided packages?

Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti at assyoma.it - info at assyoma.it
GPG public key ID: FF5F32A8

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