Re: [gentoo-user] Fun with mdadm (Software RAID)

[Alan Mackenzie <acm@muc.de>]

Hello, Wol.

On Sun, Dec 22, 2024 at 16:53:17 +0000, Wols Lists wrote:
> On 22/12/2024 15:29, Peter Humphrey wrote:
> > On Sunday 22 December 2024 13:43:08 GMT Alan Mackenzie wrote:

> >> The trouble [is] that a kernel command line, or /etc/fstab, using lots
> >> of these is not human readable, and hence is at the edge of
> >> unmaintainability.  This maintenance difficulty surely outweighs the
> >> rare situation where the physical->logical assignment changes due to a
> >> broken drive.  That's what we've got rescue disks for.

> > Hear, hear! I never could understand why everyone seems to want to jump onto
> > that band-wagon.

> I have no problem with you saying all this long guid crap makes stuff 
> unreadable (and yes, I agree, unreadable and unmaintainable aren't that 
> far different) BUT

>  > surely outweighs the rare situation where the physical->logical 
> assignment changes

> THAT DEPENDS ON YOUR HARDWARE!

> For normal consumer grade hardware, I agree. I've never known it change 
> unless I've been mucking about with add-in SATA, PATA, whatever cards.

This is the desirable state of affairs.

> BUT. Especially on big server-grade hardware, where there's lots of trip 
> switches so stuff doesn't all power up in one huge spike (and I've 
> worked with such), different parts of the system come up in a completely 
> random order, and drives re-order themselves pretty much every single boot!

So all this 32 hex digit UUID stuff is a workaround for the
unpredictability of server hardware.  What seems to be missing is a way
of associating a given disk socket on the motherboard with /dev/sda.
Instead we have to put up with "content addressing".

> So yes, with our consumer hardware I'd agree with you. But the people 
> paying big bills for reliable top-range hardware would wonder what 
> you're smoking!

I think any system admins reading this would long for the predictability
of "consumer hardware", having too often been confronted with
indistinguishable 32 hex digit identifiers.  I would imagine it quite
likely that the said admins have written scripts to make this more
manageable.

> Cheers,
> Wol

-- 
Alan Mackenzie (Nuremberg, Germany).