[arch-general] limited softraid support in AIF (WAS:Why Is My RAID Installing Failing?)

[Alexander Duscheleit]

On Thu, 14 Jan 2010 22:17:49 +0100
Dieter Plaetinck <dieter at plaetinck.be> wrote:

> On Thu, 14 Jan 2010 00:07:18 +0100
> Alexander Duscheleit <jinks at archlinux.us> wrote:
> 
> > Would it be possible to just generate the relevant mdadm.conf during
> > the configure stage without providing further additional support?
> > People are used to run installation steps in sequence so this would
> > eliminate on source of (apparently frustrating) user error.
> > 
> > A quick look at AIF's source suggest prefill_configs () as proper
> > place. I'm not certain, how AIF identifies used block devices, but
> > something like this would probably suffice:
> > 
> > if md[0-9] in $BLOCKDEVICES ->
> >       mdadm --detail --scan >> ${var_TARGET_DIR}/etc/mdadm.conf
> 
> 
> hmm. that seems simple enough. why not?
> what do you mean with $BLOCKDEVICES ? all blockdevices in the system?
> or blockdevices explicitly configured to be partionened by user? or
> blockdevices explicitly configured to be used for formatting by user?

I meant the block devices the user selected to be mounted (regardless of
formatting), so, what AIF puts in fstab mostly.
If a user wants to access a softraid from arch, he probably needs a
mdadm.conf and it wont hurt either way.

> 
> > > If the official installation guide states otherwise, we should fix
> > > that. please point me to the mistake/file a ticket.
> > > If community-maintained documentation is incorrect, fix it
> > > yourself.
> > 
> > The official istall guide specifically states that you are on your
> > own with softraid. The raid/lvm/etc wiki article is a bit twisted
> > in it's mix-and-match of methods, I shall have another look if I
> > can squeeze the relevant information in there.
> 
> the better the support in AIF gets, the smaller such articles can
> become.

I hurled a few chunks around, so at least the guide doesn't end up in
an unbootable system any more.

> 
> > > Patches to support softraid are always welcome.  Things don't get
> > > improved by merely hoping for it.
> > > http://bugs.archlinux.org/task/14149
> > 
> > WONTFIX! This is already far too easy :)
> 
> Assuming the user does the heavy work (creating the MD volumes), what
> are the other (little) tasks that AIF can implement to limit the
> amount of manual work?
> 
> - modprobe raid{1,2,3,4,5,6} ?
Should already be done by the for creating the arrays.
> - rewriting the mdadm.conf if needed (see above)
This can be done pretty indiscriminately. The conf doesn't really hurt
when it's not needed.
> - for a root filesystem which needs raid, add raid to HOOKS in
>   mkinitcpio.conf [where order is very important when combined with
>   lvm/dm_crypt etc] ?

Should be after "pata scsi sata" but before /lvm/encrypt/filesystems in
most cases. But this is not guaranteed to be safe. You could, after
all, stripe two LVs into a raid. Also, you can mix-and-match block
devices in so many ways: lvm on raid on encrypted partitions, lvm on
encrypted raid on normal partitions, encrypted lvm on raid on normal
disks, you could even encrypt each layer separately.

So I guess HOOK handling should be left to the user except when the
outcome is clear to be what we want (think premade recipes).

> 
> anything else i'm missing?
As I said, don;t go too easy on us. Where is the sense of
accomplishment when you can install arch manually in under 5 minutes?
Not to speak of fully automatic recpies.

> Dieter

Jinks
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