There is some angles of attack here:
└─zfs-import-cache.service @1min 786ms +272ms
└─systemd-udev-settle.service @494ms +1min 275ms
This is a case of "you asked for it, you got it", really. udev-settle is
a workaround for old software that wasn't written with hotplugging in
mind. It's 2016, and we really should avoid introducing new dependencies
to udev-settle, as it's conceptually broken and can't work. This
totally does not work for any hotplugged device, or a device which just
gets detected by the kernel late, or which needs to be unwrapped from
building an LVM or cryptsetup device, etc.
I think it would be much more elegant to instead create udev rules (or
systemd units) which load the ZFS cache as soon as a ZFS block device is
detected. Would that be possible/reasonable? I don't know anything about
what import-cache does, but I hope/suppose it has some way of doing this
on a per-device basis?
└─systemd-udev-trigger.service @415ms +55ms
This is cloud-init's rules for blocking udev rules until network devices
get detected and cloud-init's naming rules get applied. This is a hairy
topic and Scott and I already discussed this at length. I think there's
a better solution here, but I doubt we'll completely turn this around by
the release. This just illustrates one of the problems of the "waiting
for all hardware just to single out a particular device" approach from
above -- this waits on stuff which is completely unrelated to zfs.
** No longer affects: systemd (Ubuntu)
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https://bugs.launchpad.net/bugs/1571761
Title:
zfs-import-cache.service slows boot by 60 seconds
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