On Nov 7, 2019 15:29, Christian Reiss <email@christian-reiss.de> wrote:
Hey folks,
I am looking at setting up a hyperconverged cluster with 3 nodes (and oVirt 4.3). Before setting up I have some generic questions that I would love to get hints or even an answer on.
First off, the Servers are outfittet with 24 (SSD) drives each in a HW-RAID. Due to wear-leveling and speed I am looking at RAID10. So I would end up with one giant sda device.
Go with RAID 0 , or RAID5/6 as you will have the same data on all nodes (3 copies in total) .
a) Partitioning Using oVirt node installer which will use the full size of /dev/sda is this still the right solution to Hyperconverged given the gluster issue? If I understood it correctly gluster is using empty drives or partitions so a fully utilized drive is of no use here. Does oVirt node installer have a hyperconverged/ gluster mode? The cockpit installer can prepare the gluster infrastructure and then the oVirt cluster b) Storage Location In this 3 node cluster, creating a VM on node01 will the data for node01 always end up in the local node01 server? Nope , all data is replicated on all 3 nodes (or on 2 nodes when using 'replica 2 arbiter1' volumes). c) Starting VMs Can a VM be migrated or launched from node03 if the data resides on node01 and node02 (copies 2 with arbiter). As gluster is a shared storage, the VMs can migrate on any host that has access to the storage (in your case any of the 3 nodes). d) Efficiency / High IO Load If node01 has high IO Load would additional data be loaded from the other node which has the copy to even the load? I am aware Virtuozzo does this. Gluster Clients (in this case oVirt node) reads from all 3 nodes simultaneously for better I/O. Same is valid for writes. e) Storage Network dies What would happen with node01, node02 and node03 are operational but only the storage network dies (frontend is still alive as are the nodes). Nodes will become unoperational and all VMs will be paused until storage is restored. f) external isci/ FreeNAS We have a FreeNAS system with tons of space and fast network connectivity. Can oVirt handle storage import like remote iscsi target and run VMs on the ovirt nodes but store data there? Yep. Thank you for your time to clear this up. I have found many approaches out there that either are old (oVirt 3) or even contradict themselves (talk about RAID level...)
Cheers! -Christian