Suggestions for working with unstable nvme dev names in AWS

Polytropon freebsd at
Tue May 14 19:02:18 UTC 2019

On Tue, 14 May 2019 08:59:01 -0700, George Hartzell wrote:
> Matthew Seaman writes:
>  > On 14/05/2019 03:35, George Hartzell wrote:
>  > > Can anyone speak to the current state of device names for nvme disks
>  > > on AWS using the FreeBSD 12 AMI's?  Is name-stability an issue?  If
>  > > so, is there a work-around?
>  > 
>  > I don't know about device name stability in AWS instances, but if you
>  > are using ZFS, then shuffling the disks around should not make any
>  > difference.  With physical hardware it should be possible to eg. pop the
>  > disks out of one chassis and insert them into another in whatever order,
>  > and the system will still boot correctly.  This sounds like the virtual
>  > equivalent of that.
>  > [...]
> Thanks for the response!
> Yes, once I have them set up (ZFS or labeled), it doesn't matter what
> device names they end up having.  For now I just do the setup by hand,
> poking around a bit.  Same trick in the Linux world, you end up
> referring to them by their UUID or ....

In addition to what Matthew suggested, you could use UFS-IDs
in case the disks are initialized with UFS. You can find more
information here (at the bottom of the page):

You'll find the explanation of "UFS label", "glabel label",
and "UFS ID" there.

A description of "gpart label" is provided here:

Always remember that the different kinds of label refer to
specific things, like partitions or file systems. With ZFS
of course, this is a lot easier, and the "ZFS label" doesn't
just identify the disk device (or virtual equivalent) itself,
but includes information about its function within a ZFS

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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