Re: [pve-devel] [RFC guest-common 09/13] vzdump: schema: add fleecing property string

["DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>]

>>LVM and non-sparse ZFS need enough space for a copy for the full disk
>>up-front, so are not suitable as fleecing storages in many cases.

can't we force sparse for theses fleecing volumes, even if the storage
don't have sparse enabled ? (I can understand that it could make sense
for user to have non sparse for production for performance or
allocation reservation, but for fleecing image, it should be
exceptionnal to rewrite a full image)

>>ISCSI doesn't allow disk allocation. Should such storages be outright
>>forbidden as fleecing storages or should it just be documented?

I think it should be forbidden if it's incompatible.

>>Should the setting rather be VM-specific than backup job-specific?
>>These issues
>>mostly defeat the purpose of the default here.

can't we forbidden it in storage plugin features ? { fleecing => 1} ?

>>IIRC older version of NFS lack the ability to discard. While not
>>quite
>>as bad as the above, it's still far from ideal. Might also be worth
>>trying to detect? Will add something to the docs in any case.

I never have seen working discard with nfs, I think (never tested) it's
possible with 4.2, but 4.2 is really new on nas appliance (netapp,...).
So I think than 90% of user don't have working discard with nfs.

Is it a problem if the vm main storage support discard , but not
fleecing storage ? (I don't have looked yet how exactly fleecing is
working)

If it's a problem, I think we should forbind to use a fleecing storage
not supporting discard, if the vm have discard on 1 disk.

-------- Message initial --------
De: Fiona Ebner <f.ebner@proxmox.com>
Répondre à: Proxmox VE development discussion <pve-
devel@lists.proxmox.com>
À: pve-devel@lists.proxmox.com
Objet: Re: [pve-devel] [RFC guest-common 09/13] vzdump: schema: add
fleecing property string
Date: 29/01/2024 16:41:06

Am 25.01.24 um 15:41 schrieb Fiona Ebner:
> +    storage => get_standard_option('pve-storage-id', {
> + description => "Use this storage to storage fleecing images.
> Default is to use the same "
> +     ."storage as the VM disk itself.",
> + optional => 1,
> +    }),
> +});
> +

LVM and non-sparse ZFS need enough space for a copy for the full disk
up-front, so are not suitable as fleecing storages in many cases. ISCSI
doesn't allow disk allocation. Should such storages be outright
forbidden as fleecing storages or should it just be documented? Should
the setting rather be VM-specific than backup job-specific? These
issues
mostly defeat the purpose of the default here.

IIRC older version of NFS lack the ability to discard. While not quite
as bad as the above, it's still far from ideal. Might also be worth
trying to detect? Will add something to the docs in any case.


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