FreeBSD-10.3 root ZFS redux

[James B. Byrne]

We have eight (8) 3Tbyte drives on a system upon which I am installing
FreeBSD. The quest arises of whether one should simply grab all of
the disks or partition them to reserve a spare area. The reason put
zpool replace [-f] pool device [new_device]
Replaces old_device with new_device. This is equivalent
to attaching new_device, waiting for it to resilver, and
then detaching old_device.
The size of new_device must be greater than or equal to
the minimum size of all the devices in a mirror or raidz
configuration.
One can conceive of a 3Tb drive which has slightly more or fewer
accessible sectors than its nominal size. If the zspool incorporates
a drive with fewer accessible sectors than average for its nominal
size and one seeks to replace it with a similar drive that has more
than average for the same nominal capacity then what is the result?
Is the new drive accepted or rejected?

I managed to get this reversed in my head as I composed. The question
is what happens when a nominally 3TB HDD is put in that has fewer
accessible sectors than a similar 3TB drive already present?
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[Graham Allan]

Post by James B. Byrne
I managed to get this reversed in my head as I composed. The question
is what happens when a nominally 3TB HDD is put in that has fewer
accessible sectors than a similar 3TB drive already present?

My understanding is that it would just be rejected (I see some older
solaris examples mention a "device too small" error).

Best practice is probably to create a gpt partition of some standard
size on the drives before adding that to the pool, to give a little
adjustment room, though I confess I have made all my pools to date using
the raw drives (other than a geom label); and simply try to replace
drives with the same model.

Graham

[Martin "eto" Misuth]

On Wed, 11 May 2016 14:13:49 -0400
"James B. Byrne" <***@harte-lyne.ca>

Would you be interested in my infodump? While writing it, I realised it's quite
word heavy.

eto

[Mel Pilgrim]

Post by Graham Allan

Post by James B. Byrne
I managed to get this reversed in my head as I composed. The question
is what happens when a nominally 3TB HDD is put in that has fewer
accessible sectors than a similar 3TB drive already present?

My understanding is that it would just be rejected (I see some older
solaris examples mention a "device too small" error).
Best practice is probably to create a gpt partition of some standard
size on the drives before adding that to the pool, to give a little
adjustment room, though I confess I have made all my pools to date using
the raw drives (other than a geom label); and simply try to replace
drives with the same model.

You need to do this anyway for root on ZFS without other storage in the
system because of the freebsd-boot partition.