Comment 21 for bug 1832859

(In reply to Renaud Métrich from comment #7)
> I must be missing something. This service is used to deactivate "remote"
> block devices requiring the network, such as iscsi or fcoe.

Nope, ALL storage, remote as well as local, if possible. We need to look at the complete stack (e.g. device-mapper devices which are layered on top of other layers, are set up locally)

> Why aren't these services deactivating the block devices by themselves?

Well, honestly, because nobody has ever solved that :)

At the beginning, it probably wasn't that necessary and if you just shut your system down and let the devices as they are (unattached, not deactivated), it wasn't such a problem. But now, with various caching layers, thin pools... it's getting quite important to deactivate the stack properly to also properly flush any metadata or data.

Of course, we still need to count with the situation where there's a power outage and the machine is not backed by any other power source so you'd have your machine shot down immediately (for that there are various checking and fixing mechanism). But it's certainly better to avoid this situation as you could still lose some data.

Systemd's loop in the shutdown initramfs is really the last-resort thing to execute, but we can't rely on that (it's just a loop on device list with limited loop count, it doesn't look at the real nature of that layer in the stack).