Comment 10 for bug 1555938
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| Michal Dulko (michal-dulko-f) wrote | #10 |
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0e1f616
(Get the code!)
I think we need to take one step back and think of why "disable" was introduced in the first place. We've inherited it when Cinder was forked out of Nova. In Nova the use case is to implement a pattern for host maintenance:
1. Set host to disabled. No new VMs will be scheduled there.
2. Start to live-migrate VMs out of host.
3. When finished patch the host, reboot it and enable it again.
Now that's useful also in Cinder - when running an LVM driver.
Having that in mind - should cloning a volume or snapshot creation go through scheduler? I don't think so, as you cannot create a snapshot from a different host. Moreover it's better to give user feedback that service is disabled directly from the API.
From the other hand implementing a check in the API that blocks disabled services will decrease availability of volumes that are placed on disabled host in the maintenance window. I wonder what happens for example with snapshots when volume is migrated? Are they migrated to other backend as well?