On Wed, Jul 7, 2021 at 6:54 PM Anatoliy Radchenko
wrote:
>
Adding back users@ovirt.org. We want to keep the discussion public
and searchable.
> But,thinking,
> in case you want to create the data domain posix compliant with a block in 4k
> you cannot do this because you still have 512 block on engine and gives an
> error about the incompatibility of 512 and 4k.
posix data domain is just NFS data domain under the hood, with
modified mount options, so it share the same limits of NFS data
domain.
I'm not sure how do you get the compatibility issue - do you mean provisioning
engine on a host with 4d disk (using libvirt and local storage) and then copying
to data domain created on same local storage (512 bytes sector size)?
> How to be in this case?
I think this should work as is since the bootstrap vm created using libvirt
is using 512 bytes sector size, regardless of the underlying storage sector
size (qemu hides the actual sector size from the vm). So the vm starts
with 512 bytes sector size, and them move to another storage which again
have 512 bytes sector size.
This also works when the other storage uses 4k sector (e.g hyperconverge
using gluster and vdo) size since again qemu hides the underlying storage
sector size.
> Il giorno mer 7 lug 2021 alle ore 17:45 Anatoliy Radchenko
> ha scritto:
>>
>> Hi Nir,
>> with transferring engine I meen to move it after installation to hosted
>> engine storage domain, but not important.
>> In any case thank you for your response, everything is just as I thought.
>> Regards
>>
>> Il giorno mer 7 lug 2021 alle ore 17:32 Nir Soffer ha
>> scritto:
>>>
>>> On Wed, Jul 7, 2021 at 5:58 PM wrote:
>>> > With some installations of Ovirt in the configuration of ssd for boot OS
>>> > and hdd (4k) for data domain, engine is installed on ssd with a block
>>> > size of 512e and then transferred to hdd 4k.
>>>
>>> What do we mean by transferring engine to another disk?
>>>
>>> Engine is installed either on a host, or in a vm. On a vm, it always
>>> using sector
>>> size of 512 bytes, since we don't support vms with sector size of 4k. If
>>> enigne
>>> in installed on a host, there is no such thing as "transfer" to
>>> another host. You
>>> can reinstall engine on another host and restore engine database using a
>>> backup. Sector size does not matter in this flow.
>>>
>>> Sector size for data domain is relevant only for gluster storage or
>>> local storage.
>>> These are the only storage domain types that can use 4k storage.
>>>
>>> > and if I wanted to leave the engine on ssd (in a separate partition which
>>> > will also have a size of 512e), I encountered an incompatibility error
>>> > between block sizes 512 and 4k (example glusterfs or when the data domain
>>> > was configured as posix compliant fs). NFS domain passed.
>>> > As I understand it, the NFS uses 512e as well as the drivers of the guest
>>> > machines,
>>>
>>> Yes, NFS is always using a sector size of 512 bytes since we don't
>>> have any way to
>>> detect the underlying device sector size.
>>>
>>> > and a VM created on a domain with a 4k block will still have 512e. As a
>>> > result, we have a block of size 512 in any case.
>>>
>>> Yes, vms always see sector size of 512 bytes. qemu knows the underlying
>>> storage
>>> sector size and align I/O requests to the underlying storage sector size.
>>>
>>> > Does it make sense to use devices with a 4k block at the present time? Is
>>> > there any configuration to take advantage of 4K?
>>>
>>> Yes, the most attractive use case is VDO, which is optimized for 4k sector
>>> size.
>>>
>>> Another use case is having disks with 4k sector size which may be cheaper or
>>> easier to get compared with disk supporting 512e.
>>>
>>> For block storage oVirt does not support devices with 4k sector size yet.
>>>
>>> Nir
>>>
>>
>>
>> --
>> _
>>
>> Radchenko Anatolii
>> via Manoppello, 83 - 00132 Roma
>> tel. 06 96044328
>> cel. 329 6030076
>>
>> Nota di riservatezza : ai sensi e per gli effetti della Legge sulla Tutela
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>> mittente.
>
>
>
> --
> _
>
> Radchenko Anatolii
> via Manoppello, 83 - 00132 Roma
> tel. 06 96044328
> cel. 329 6030076
>
> Nota di riservatezza : ai sensi e per gli effetti della Legge sulla Tutela
> della Riservatezza Personale (Legge 196/03) si precisa che il
