[ovirt-users] Re: Direct LUNs and VM Pauses

Vdsm does monitor multipath events for all LUNs, but they are used only > for reporting purposes, see: > > https://ovirt.org/develop/release-management/features/storage/multipath-e... > > We could use the events for resuming vms using the multipath devices that > became available. This functionality will be even more important in the > next version > since we plan to move to LUN per disk model. > > I will look at doing this. At the very least I feel that differences/limitations between storage back-ends/methods should be documented. Just so users don't run into any surprises.

My other question is, how can I keep my VMs with Direct LUNs from pausing >> during short outages? Can I put configurations in my multipath.conf for >> just the wwids of my Direct LUNs to increase the ‘no_path_retry’ to prevent >> the VMs from pausing in the first place? I know in general you don’t want >> to increase the ‘no_path_retry’ because it can cause timeout issues with >> VDSM and SPM operations (LVM changes, etc). But in the case of a Direct LUN >> would it cause any problems? >> > > You can add a drop-in multipath configuration that will change > no_path_retry for specific device, or multiapth. > > Increasing no_path_retry will cause larger delays when vdsm try to > access the LUNs via lvm commands, but the delay should be only on > the first access when a LUN is not available. > > Would that increased delay cause any sort of issues for Ovirt (e.g. thinking a node is offline/unresponsive) if set globally in multipath.conf? Since a Direct LUN doesn't use LVM, would this even be a consideration if the increased delay was limited to the Direct LUN only?