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