Re: Automatically start two-level mdadm RAID arrays (i.e. RAID 60) on boot?

[Roman Mamedov <rm@romanrm.net>]

On Thu, 15 Feb 2018 15:41:37 -0500
Sean Caron <scaron@umich.edu> wrote:

> Hi all,
> 
> My site is very happily using MD RAID arrays constructed in two
> levels. That is to say, we do RAID 60 by constructing an mdadm RAID 0
> out of a number of mdadm RAID 6 strings.
> 
> These work great but one thing we have found and been living with is
> that, when the system boots, mdadm will automatically start all the
> RAID 6 strings, but it will not automatically start the top level RAID
> 0 container. The machine pauses on boot ("Hit S to skip, M to manually
> resolve") trying to mount the RAID because the device is not
> available, and a sys admin needs to manually go to the console and
> start the top level RAID 0 to continue the boot.

I had RAID5/6 with some members being RAID0s. IIRC it was a simple matter of
listing them in the correct order of initialization in mdadm.conf. Not sure if
this was strictly required, just that I did so right away (expecting that it
would be), and everything simply worked.

On the other hand, these days you likely have systemd, and it never misses its
chance to make people's lives much more interesting than that.

-- 
With respect,
Roman