Re: What's the typical RAID10 setup?

[Stan Hoeppner <stan@hardwarefreak.com>]

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.

> http://www.snia.org
> 
> The RAID levels are defined in DDF - a "SNIA" standard.

Exactly.  It's an SNIA standard.  Unfortunately SNIA doesn't carry sufficient
weight to drive full adoption.  I commend them for trying though.

> http://www.snia.org/tech_activities/standards/curr_standards/ddf/
> 
> (Info courtesey of Neil Brown)

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?"

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.

-- 
Stan
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html