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partman-zfs && ZoL

I'm trying to re-add the ZoL stuff I made a year and a half ago (we're 'expecting'
ZoL to be accepted 'soon' - it's now in the hands of the legal department, we finally
got the reject we where expecting).

While testing this out (setting up a local, authenticated repo haven't been easy!),
I noticed that partman-zfs (or 'someone') is creating a msdos label and ONE partition
on the disk(s) I choose and use that partition for the ZFS device.

In, at least ZoL (but I expect that be generic ZFS), this isn't recommended. By using
a partition (and not a whole disk - GPT with two partitions, 1 and 9), you loose the
[disk] caching support. Meaning, it's a lot slower…

Having the whole disk allows ZFS to make assumptions and optimizations that are not
possible if it has to share the disk (as indicated by being given a partition).

Trying to find a better way to put this, I googled "zfs whole disk versus partition"
and the second hit was this thread (which indicates that even kFreeBSD could benefit
from this):


What's worse is that if I go through the installer again (destroying the pool before
I choose 'Manual partitioning', I only get to choose the partitions. The disk device
(/dev/sdX on Linux) isn't shown, forcing me to create the pool with partition, not

Could anyone give me some pointers on where/how to change that? I just can't find the
part in partman-zfs that creates the label and partition…

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