[PVE-User] Discard transmission between VM / LVM / mdadm layers ?

[Olivier Benghozi]

In fact if you use the debian installer you have to take care of the creation of the data lvs (and in fact, of the general partitioning scheme) yourself (and not accept what the debian installer does by default). The lvs-thin data volume must be created manually after install (and therefore most of the space must be left free at the install – and you'd better create it with 16GB metadata space to avoid horror stories later).

By example this is what we can find here (installed using debian buster installer):

# lsblk (edited)
NAME                         MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda                            8:0    0   1.8T  0 disk 
├─sda1                         8:1    0   512M  0 part /boot/efi
├─sda2                         8:2    0   488M  0 part /boot
└─sda3                         8:3    0   1.8T  0 part 
  ├─pve-root                 253:0    0 186.3G  0 lvm  /
  ├─pve-swap                 253:1    0   7.5G  0 lvm  [SWAP]
  ├─pve-data_tmeta           253:2    0  15.8G  0 lvm  
  │ └─pve-data-tpool         253:4    0   1.5T  0 lvm  
  └─pve-data_tdata           253:3    0   1.5T  0 lvm  
    └─pve-data-tpool         253:4    0   1.5T  0 lvm  

# lvs -a
  LV              VG  Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  data            pve twi-aotz--  <1.53t             0.35   0.16                            
  [data_tdata]    pve Twi-ao----  <1.53t                                                    
  [data_tmeta]    pve ewi-ao----  16.00g                                                    
  [lvol0_pmspare] pve ewi-------  16.00g                                                    
  root            pve -wi-ao---- 186.26g                                                    
  swap            pve -wi-ao----  <7.45g


> Le 13 déc. 2019 à 16:52, Frédéric MASSOT <frederic at juliana-multimedia.com> a écrit :
> 
> Ah, there is the subtlety, lvm-thin transmits discard/trim commands, but
> not lvm. It is therefore necessary to use the storage type lvm-thin and
> not lvm.
> 
> I installed the server with the Debian installer and then I installed
> Proxmox. The Debian installer uses the type lvm and not lvm-thin.
>