Re: wish for Linux MD mirrored raid types

["Keld Jørn Simonsen" <keld@keldix.com>]

On Mon, May 09, 2011 at 01:22:42PM +0800, Emmanuel Noobadmin wrote:
> On 5/6/11, Keld Jørn Simonsen <keld@keldix.com> wrote:
> > Hi List
> >
> > based on the recent discussion, that showed lacking knowledge
> > on Linux MD RAID10 features, I have some thoughts:
> >
> > It is really hard to disseminate information on "new" features
> > in MD RAID. RAID10 has been in the kernel since 2.6.9 - from 2004.
> > I have tried to give info on RAID10 at a number of web pages,
> > and still many people, even on our linux-raid list are not aware
> > of it.
> >
> > Also many people are confused about Linux MD raid10 and RAID1+0.
> >
> > So I think we shopuld rather name things in another way.
> >
> > I would like linux MD raid10 functionality to be part of the Linux MD
> > RAID1 module, and be called raid1. This is in accordance with the
> > use of the RAID1 term as standadized by SNIA. In fact the RAID10-offset
> > layout is an implementation of a SNIA RAID specification. The RAID10-near
> > layout is an implementation of a simple RAID layout. And the RAID10-far
> > layout is just another layout far a mirrored RAID.  So all these types
> > could just be defined as different RAID1 layouts.
> 
> Giving my noob's 2 cents worth although I haven't followed the
> original discussion. As a noob,  I think doing this will just confuse
> us more.
> 
> There are plenty of existing materials around for those of us who try
> to figure things out by googling. As it is, our (or maybe just me)
> understanding is Linux RAID 1 is just like every other raid 1: simple
> and straightforward, 2 drives mirroring each other.
> 
> This is is also usually the level that most of us start with. If the
> instructions are short, easy to understand and simple to implement, we
> usually gain confidence in using it and exploring mdraid further.
> 
> Most of us noobs are also aware that RAID 10 is more complicated and
> there are two versions, i.e. 1+0 and 0+1. So psychologically, I had no
> problems accepting that once I looked into it, there were much more
> complex stuff and all these possible layouts: mdraid is cool!
> 
> Now, if RAID 10 was renamed to RAID 1, with the corresponding change
> in documentation, what's going to happen for us noobs is this: "Omg,
> why are there so many different versions and options just for raid 1?"
> and importantly "Why is this manual/wiki different from the tons of
> other pages about using mdraid 1?" For some, this would mean mdraid is
> too difficult even for raid 1, mdraid is not cool! :)
> 
> So newbies will get more confused/frustrated as a result.
> 
> Personally, I had to spend some time figuring out (I'm noob and I'm
> not very smart) the different layouts from the examples on wiki. This
> is because there wasn't enough examples, at least to me, to clearly
> show what's the difference if more/less disks were used. So for me,
> and other noobs, it would probably help if the wiki had more examples
> of each layout, maybe graphics to show the difference since it's
> probably easier to see things if they were colour coded blocks rather
> than stuff like A1 a1 A2 a2.
> 
> This and perhaps more elaboration on the difference between mdraid 10
> and normal raid 10  would probably be better to clear up confusion
> than renaming something we might have some familiarity with, into
> something we also already have familiarity, resulting in something
> that contradicts existing familiarity.

I see your point. Given Neil's input I think we should  rateher call it
raid1e.

Best regards
keld
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