disklabel differences FreeBSD, DragonFly

Alex Zbyslaw xfb52 at dial.pipex.com
Fri Jul 28 00:01:03 UTC 2006

Mike Meyer wrote:

>>>>A further reason to separate partitions is that dump works at the level 
>>>>of a partition.  Different partitions may have very different backup 
>>>>requirements, and for those of us without huge tape drives, partitioning 
>>>>to a size that can be dumped on one tape makes life easier.
>>>That's one of the technical reasons I mentioned in the part you
>>>didn't quote.
>>To my mind, it only takes *one* technical reason.  If I need multiple 
>>partitions to make backups easy, then arguments about log files are 
>>irrelevant :-)
>If you're going to count 1, 2, many, then we already have "many"
>partitions, and don't need more. Once you get into finer distinctions
>of "many", you need to figure out which reasons are actually valid,
>and which are spurious, so you can pick from among those manys.

I have no real idea what this means, sorry.  It seems to me that whoever 
made the initial decision to stop at 8 (size of an integer?) clearly 
thought counting past 2 was worthwhile.  Maybe the original reasons no 
longer apply since quite a lot has changed since then :-)

>>>Well, there are always special cases. But hardware is so cheap these
>>>days, I'm used to fine-tuning the *system*, not just the partition.
>>>If something is so critical that it needs it's own partition, it's
>>>probably so critical that it needs it's own system as well. In fact,
>>>most of the thing I work on these days are so critical that they need
>>>several systems, half of them at a second site with automatic failover
>>>between them.
>>Not everyone is in a position to throw money at everything and what's 
>>cheap to you isn't cheap to everyone.
>Boxes are cheaper than disk space - my last two low-end boxes cost
>less than my last small disk drive, even though I ordered them all
>about the same time. If you can afford the disk for some process, then
>chances are good you can afford a system instead, or as well.
I don't understand this either.  Surely the box has to include the disk 
space so how can it cost less?  If it costs less because it's a cheap 
piece of junk, why would I even want it?

And the "cost" of the system doesn't stop at the up front price - 
running costs including maintaining the box surely count (not to mention 
that I have nowhere to put the damn thing).  And I'm not sure where 
needing a separate partition and criticality became the same thing.  I 
don't claim to want or need separate partitions because any particular 
subset of the filesystem is critical, but because I want it to be 
separate for at least the two reasons outlined below.

>>I can't possibly justify one system for everything that needs a
>>partition, nor do I even feel the need to do that.  If anything, it
>>would be a major inconvenience.
>My claim is that your "everything that needs a partition" probably
>includes things that don't. But to prove that, we need to examine the
>reasons you think those things need a partition. I believe the only
>one you've given so far - as a space firewall - is specious.
Except that we also have the "dump", and the "different params for 
different parts of the filesystem" arguments.  I think you agreed that 
you counted those as technical reasons.

>Your arguments remind me of the environments I worked on in the 70s
>and 80s. Minis and mainframes that did all the computing for an
>organization. All the daemons that talked to the outside world ran on
>the same box as the developers ran compiles and tests on, etc. While
>that worked really well when it came to generating a robust OS, I
>haven't seen an environment like that in decades. Hell, most of my
>clients would shit bricks at the thought of putting their source or
>data on a machine that could be reached from the internet at large at
>all. Every developler has a box - or three - on their desks. The ETL
>boxes are distinct from the database boxes are distinct from the
>internal mail server is distinct from the external mail server,
>etc. If I want to have a process send email notices about something, I
>usually have to beat on them if I want a mail server on the box. And
>so on....
Fine.  You have access to lots of money and infrastructure.  I don't.  
Throwing money at a problem is not a solution available to everyone.

>>>Frankly, if you're really worried about
>>>bootable slices, you should be advocating giving FreeBSD the ability
>>>to boot from a logical volume.
>>Who said I didn't?  I have no objection to such a facility and would 
>>welcome it.  It just imagined that extending the number of partitions 
>>from 8 to 16 would have been easier than booting from logical slices.  
>>If booting from logical slices is easier then I'm all for it.
>You're not asking the right question just yet. The question shouldn't
>be "which is easier to add", but "which provides the most benefit for
>the least pain" (which subsumes the pain involved in adding it). I
>believe that the benefits of adding more partitions per slice are
>minimal - there are at least three ways to add more file systems that
>aren't bootable, and there's a better fix to the problem of wanting
>more bootable partitions - and the pain involved in upgrading a system
>across a change in the bsdlabel would be rather high.
This all sounds fine to me, though the OP who wanted to mount a 
DragonFly partition might disagree :-(

The bottom line for me is this: if the number of partitions per slice 
were to increase from 8 to 16, that would make my life easier as I do 
things now.  The way I do things now works very well for me. and nothing 
you have said tells me how I could do things differently and still have 
it work as well.   If no-one is going to increase partitions from 8 to 
16, I'll survive.  If someone instead makes logical partitions bootable, 
I'd be happy too.  If someone comes up with something completely 
different that makes it easier for me to boot multiple FreeBSD's on a 
single machine without a) adding extra disk or b) buying expensive 
software, I'd be thrilled to bits.

>there are at least three ways to add more file systems that
>aren't bootable,
Logical partitions.  What would be your other two?  (Off list, if you 
prefer and can be bothered to answer, since it has got rather OT).


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