Re: [PVE-User] LVM question

[Leandro Roggerone <leandro@tecnetmza.com.ar>]

Thanks !! very helpful.


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El lun, 12 abr 2021 a las 3:48, Dominik Csapak (<d.csapak@proxmox.com>)
escribió:

> Hi,
>
> On 4/9/21 19:19, Leandro Roggerone wrote:
> > Hi guys , after install a new storage to my box , had to create lvm-thin.
> > Im not very good with lvm , after reading some docs , and links like:
> >
> https://forum.proxmox.com/threads/how-to-create-an-lvm-thinpool-and-vz-directory-on-the-same-disk.62901/
> >
> > I got a working solution  but have also some questions about it.
> > This is what I did:
> >
> >   wipefs -a /dev/sdb
> >
> > sgdisk -N 1 /dev/sdb
> >
> > pvcreate --metadatasize 1024M -y -ff /dev/sdb1
> >
> > vgcreate --metadatasize 1024M proxvg /dev/sdb1
> >
> > lvcreate -l 100%FREE --poolmetadatasize 1024M --chunksize 256 -T -n
> > proxthin proxvg
> >
> > lvcreate -n proxvz -V 1.1T proxvg/proxthin
> >
> > mkfs.ext4 /dev/proxvg/proxvz
> >
> > mkdir /media/vz
> >
> > echo '/dev/proxvg/proxvz /media/vz ext4 defaults,errors=remount-ro 0 2'
> >>
> > /etc/fstab
> >
> > mount -a
> >
> >
> > And have following result:
> >
> >
> > root@pve2:~# lvs
> >    LV            VG     Attr       LSize    Pool     Origin Data%  Meta%
> >   Move Log Cpy%Sync Convert
> >    proxthin      proxvg twi-aotz--    1.63t                 22.03  6.34
> >
> >    proxvz        proxvg Vwi-aotz--    1.10t proxthin        1.67
> > root@pve2:~# lvdisplay
> >    --- Logical volume ---
> >    LV Name                proxthin
> >    VG Name                proxvg
> >    LV UUID                4cEIr9-3ZVQ-vsy1-q9ZX-GsaD-7oq0-pZixsX
> >    LV Write Access        read/write
> >    LV Creation host, time pve2, 2021-04-01 13:09:41 -0300
> >    LV Pool metadata       proxthin_tmeta
> >    LV Pool data           proxthin_tdata
> >    LV Status              available
> >    # open                 3
> >    LV Size                1.63 TiB
> >    Allocated pool data    22.03%
> >    Allocated metadata     6.34%
> >    Current LE             428451
> >    Segments               1
> >    Allocation             inherit
> >    Read ahead sectors     auto
> >    - currently set to     256
> >    Block device           253:2
> >
> >    --- Logical volume ---
> >    LV Path                /dev/proxvg/proxvz
> >    LV Name                proxvz
> >    VG Name                proxvg
> >    LV UUID                huzpPT-g0Gd-3Jwb-2ydz-InHh-73vN-Jnc5TR
> >    LV Write Access        read/write
> >    LV Creation host, time pve2, 2021-04-01 13:10:12 -0300
> >    LV Pool name           proxthin
> >    LV Status              available
> >    # open                 1
> >    LV Size                1.10 TiB
> >    Mapped size            1.67%
> >    Current LE             288359
> >    Segments               1
> >    Allocation             inherit
> >    Read ahead sectors     auto
> >    - currently set to     256
> >    Block device           253:4
> >
> >
> > Have following comments:
> >
> > I can create VMs on proxthin partition so it is ok.
> >
> > I can create backup on  proxvz partition so it is ok.
>
> Looks OK imho.
>
> >
> > What im concerned about is:
> >
> > Physic storage space is about 1.8TG , how is it possible to create a 1.6
> > and 1.1T volumnes inside ?
>
> LVM Thin is 'thin-provisioned' it only uses space when it is really
> written.
>
> > It can be a problem in the future ?
>
> yes, if you do not monitor your real usage, if the thinpool runs full,
> you can lose data.
>
> > I was thinking about reduce proxthin partition to 600Gb aprox , so it
> make
> > same sense 1.1T + 600G aprox 1.8 T
> > But there is no LV Path on proxthin partition so I can unmount and the
> > reduce.
> > So ..
> > What im missing here ? do I need to reduce proxthin partition ( I do need
> > the 1.1T partition to backup).
>
> the LV 'proxvz' is inside the thinpool 'proxthin' so as long as you
> never allocate more that ~500GiB of vm/ct volumes, it should be fine.
>
> alos, on allocation, the thinpool will print warnings if the allocated
> lvs are bigger than the space available
>
> hope this helps
>
> > Hope to be clear about this guys.
> > Any comment would be wellcome.
> > Leandro.
> > _______________________________________________
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> >
> >
>
>
>