Re: What's the typical RAID10 setup?

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

On Thu, Feb 03, 2011 at 05:43:42PM -0600, Stan Hoeppner wrote:
> Keld Jørn Simonsen put forth on 2/3/2011 5:04 AM:
> > On Mon, Jan 31, 2011 at 06:58:29PM -0600, Stan Hoeppner wrote:
> >> Jon Nelson put forth on 1/31/2011 3:27 PM:
> >>> Before this goes any further, why not just reference the excellent
> >>> Wikipedia article (actually, excellent applies to both Wikipedia *and*
> >>> the article):
> >>>
> >>> http://en.wikipedia.org/wiki/Non-standard_RAID_levels#Linux_MD_RAID_10
> >>>
> >>> The only problem I have with the wikipedia article is the assertion
> >>> that Linux MD RAID 10 is non-standard. It's as standard as anything
> >>> else is in this world.
> >>
> >> Unfortunately there is no organization, no standards body, that defines RAID
> >> levels. 
> > 
> > Well there is an organisation that does just that, namely SNIA.
> 
> I should have qualified that with "defines RAID levels the entire industry
> accepts/adopts".  Unfortunately SNIA is not a standards body or working group,
> such as PCI-SIG, or IETF, whose specifications entire industries _do_ accept/adopt.

I don't know about SNIA, but I have vast experience with standardisation
bodies. I see SNIA as an industry standard standardisation body. I don't
know how pervasive that organisation is, but their membership list is
impressive http://www.snia.org/member_com/member_directory/ -
Looks like everybody in the harddisk business is on board.

> Please note that the SNIA Disk Data Format document doesn't define RAID 10 at
> all.  Yet there is a single mention of RAID 10 in the entire document:
> 
> "RAID-1E 0x11 >2 disk RAID-1, similar to RAID-10 but with striping integrated
> into array"
> 
> They don't define RAID 10, but they reference it.  Thus one can only assume that
> SNIA _assumes_ RAID 10 is already well defined in industry to reference it in
> such a manner without previously defining it in the document.
> 
> Does anyone else find this reference to a RAID level omitted in their
> definitions a little more than interesting?  This RAID 10 omission is especially
> interesting considering that RAID 10 dominates the storage back ends of Fortune
> 1000 companies, specifically beneath databases and high transaction load systems
> such as enterprise mail.
> 
> They've omitted defining the one RAID level with the best combination of high
> performance, most resilience, and greatest penetration of the "high end" of
> computing in the history of RAID.  This begs the question:  "Why?"

Well RAID1+0 is not the best combination available. I would argue that
raid10,f2 is significantly better in a number of areas.

> Something smells bad here.  Does one of the RAID companies own a patent or
> trademark on "RAID 10"?  I'll look into this.  It just doesn't make any sense
> for RAID 10 to be omitted from the SNIA DDF but to be referenced in the manner
> it is.

It looks like they do define all major basic RAID disk layouts. (except
raid10,f2 of cause) . RAID1+0 is a derived format, maybe that is out of
scope of the DDF standard.

Best regards
keld
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