[dm-crypt] KISS (was disappearing luks header and other mysteries)

Boylan, Ross Ross.Boylan at ucsf.edu
Tue Sep 16 02:53:21 CEST 2014


[switching edresses]
<Arno>
If I see this correcly, you have

1. Partition
2. RAID
3. LVM 
4. LUKS

That is decidedly too many. KISS is not even in the building
anymore with that. I know, likely the distro gave you something 
like this, but really it is a symptom of a failed enginering 
mind-set that keeps stacking up complexity until things fail.
</Arno>

It's not simple regardless of whether or not LVM is in the mix.  It's certainly true that every layer adds complexity, but I don't see a good alternative given my needs, which include regularly growing file systems and creating and deleting underlying devices for file system and virtual disks.

Since I now have the "opportunity" to rebuild the system I can change how I approach things.  But the reasons for the original design still seem valid.

One consideration may be less pressing now: I did RAID over partitions, not RAID over disks, so that there was a way to bootstrap the system start.   grub may not need that; OTOH with GPT the recommendation is to reserve some initial space for the boot loader; if I do that I'll be left with RAID-1 over partitions.

To some extent the layers are the result of the Unix philosophy of having tools focused on one thing; each layer has a different goal.

Obviously something went wrong this time, and since the symptom is at the level of LVM volume groups it's possible it was an LVM bug, perhaps triggered by allocating all available space and writing to it (did that with both volume groups).  But that's speculative, and it seems more likely either the mistake I know I made or some other I don't know about is the cause.  Since the software was old, newer software may resolve some bugs (or introduce others!).

I do plan to stick with 0.90 for RAID.

Ross
 


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