Backup and the replication - Functioning/Scale

Pilow

@fcgo when adding an XOPROXY to a job, it flows from XOPROXY to the remote
I think XOA is not involved, checked the network bandwidth, xoa was sleeping

XOPROXY read/writes from source remote to destination remote

fcgo

@Pilow I was asking in the case where the sites are only allowed to communicate via HTTPS, meaning NFS remote at site 1 is accessible through proxy 1, and NFS remote at site 2 is accessible through proxy 2 (XOA being on site 1).

Pilow

@fcgo this is where you reach a limit...
in an XOA backup copy job configuration, you select the proxy, and it drives source AND destination

you cannot have a proxy for SOURCE and a proxy for DESTINATION

Pilow

but each remote (SOURCE and DESTINATION) can be attached to the same proxy... so, the proxy read/writes

and you have to manage your network accordingly so that this proxy can reach each remote (here goes the static routing or vpns...)

fcgo

@florent can you confirm for the replication job ?

Thank you

florent

@fcgo it goes from xapi (= pool/hosts) to xapi , and xapi to remote as of now, you can't chain proxy .

xapi call uses https, that means that replication accross sites uses https . If you do backup, and your backup is in the same site as your NFS, then the xapi<-> proxy path is in https, and the proxy <-> NFS will be local

that is one of the strength ( and complexity ) of xcp-ng infra : everything go through an API ( the xapi ) nobody access host/pool data directly from the outside

fcgo

@florent Hi,

Thank you.

And during backup which host is working hard during the vdi export to XOA (or to the proxy) : is it the host which contains the backed up VM, or is the master also doing some work (other than control channel calls) ? Through which host the network flow is going through ?

florent

@fcgo if the storage is shared : the export is done by one of the host of the pool
If the storage is not the export is done by the host with the storage . Same for the host receiving the data

The command channel, as you said, is always the master to the xoa (and eventually xo-proxy)

So for a replication :

[source SR] => source host =https export call=> xoa / xo-proxy =https import call=> target host => [target SR]

if the xoa is running on the host doing an export, it does not use the physical network
the network use between the host and SR is dependent on the storage used

fcgo

@florent "the export is done by one of the host of the pool"
How is this host selected ? Is it the master one, the one hosting the VM, or the less busy one in case of shared storage ?

fcgo

@florent did you have the the time to check my last question related to how the host (doing the export) is selected ?

Br,

florent

@fcgo AFAIK the host is selected as random maybe @andriy.sultanov know more

andriy.sultanov

@florent @fcgo the host that was queried (with host_ip/export_raw_vdi) will do the export from the shared SR, and will redirect the query to the host that can see the SR otherwise. So it's up to the XO/other orchestrators if they want to distribute the load here.