Proposal for a new disk configuration utility

[Michael Tautschnig]

> > For those of you who are already using LVM/RAID: Please check,
> > whether the format described below allows for configuring your exact
> > setup using FAI - thanks!
> 
> Looks like it supports everything the old one supported, except:
> 
>  1. RAID - name metadevices and support nesting
> 
>     Previously you could set up a raid 10 device with just RAID 0 + 1
>     modules.  Just define your raid 0's, then use those metadevices as
>     components of a raid 1.  Would that be possible?
> 
Yes, I think we should allow for that, but the implementation must take care of
possible recursion...

>     Also you used to be able to specify which metadevice each one is.
>     Normally you only care for consistency.  These problems are
>     perhaps peripherally related.
I'm not entirely sure, whether I understood that correctly: Are you talking
about explicit numberings of the devices? My idea was to make the way the RAID
config works as similar as possible to the configuration of physical disks,
where the numbers are set implicitly by the ordering as well.

> 
>  2. Support optional specification of a PV to put a volume on.
> 
>     The script I wrote allowed you to do this.  For instance you might
>     use one bug VG for flexibility, but specify that certain
>     partitions end up on one physical volume seperate.  For example
>     database journal volumes are often moved onto seperate disksets
>     for busy OLTP servers.  However, you don't want to set up seperate
>     VGs for them because then you can't move LVs between them.

Actually I didn't even know that this is possible... I'll put this in my notes.

> 
> Otherwise, I like the fact you're using EBNF to specify, makes
> implementing it look more tempting :).
> 
> Actually reading the EBNF I think you've got the latter concern
> covered; is that what is intended with this rule?
> 
>   type ::= primary
>            /* for physical disks only */
>            | logical
>            /* for physical disks only */
>            | raid[015]
>            /* raid level */
>            | [^/[:space:]]+:[^/[:space:]]+
>            /* lvm logical volume: pv name and lv name*/
>

What do you mean by "the latter concern"? I'm not really sure what I am to tell
you here!?

Thanks a lot for your input,
Michael

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