[ovirt-users] Re: blok size and 512e and 4k

On Wed, Jul 7, 2021 at 6:54 PM Anatoliy Radchenko <radchenko.anatoliy(a)gmail.com&gt; wrote: Adding back users(a)ovirt.org. We want to keep the discussion public and searchable. 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)? 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 <radchenko.anatoliy(a)gmail.com&gt; 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 <nsoffer(a)redhat.com&gt; ha scritto: >>>>> On Wed, Jul 7, 2021 at 5:58 PM <radchenko.anatoliy(a)gmail.com&gt; 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 della Riservatezza Personale (Legge 196/03) si precisa che il presente messaggio, corredato dei relativi allegati, contiene informazioni da considerarsi strettamente riservate, ed è destinato esclusivamente al destinatario sopra indicato, il quale è l'unico autorizzato ad usarlo, copiarlo e, sotto la propria responsabilità, diffonderlo. Chiunque ricevesse questo messaggio per errore o comunque lo leggesse senza esserne legittimato è avvertito che trattenerlo, copiarlo, divulgarlo, distribuirlo a persone diverse dal destinatario è severamente proibito,ed è pregato di rinviarlo al 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 presente messaggio, corredato dei relativi allegati, contiene informazioni da considerarsi strettamente riservate, ed è destinato esclusivamente al destinatario sopra indicato, il quale è l'unico autorizzato ad usarlo, copiarlo e, sotto la propria responsabilità, diffonderlo. Chiunque ricevesse questo messaggio per errore o comunque lo leggesse senza esserne legittimato è avvertito che trattenerlo, copiarlo, divulgarlo, distribuirlo a persone diverse dal destinatario è severamente proibito,ed è pregato di rinviarlo al mittente.