From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen Subject: Re: What's the typical RAID10 setup? Date: Fri, 4 Feb 2011 10:06:03 +0100 Message-ID: <20110204090602.GA4017@www2.open-std.org> References: <4D4718E1.9040607@hardwarefreak.com> <20110131203725.GB2283@www2.open-std.org> <4D475AB5.10600@hardwarefreak.com> <20110203110428.GA26762@www2.open-std.org> <4D4B3DAE.3070502@hardwarefreak.com> <20110204070613.GA3788@www2.open-std.org> <4D4BB87A.30800@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <4D4BB87A.30800@hardwarefreak.com> Sender: linux-raid-owner@vger.kernel.org To: Stan Hoeppner Cc: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen , Jon Nelson , Mathias =?iso-8859-1?Q?Bur=E9n?= , Roberto Spadim , Denis , Linux-RAID List-Id: linux-raid.ids On Fri, Feb 04, 2011 at 02:27:38AM -0600, Stan Hoeppner wrote: > Keld J=F8rn Simonsen put forth on 2/4/2011 1:06 AM: >=20 > > Well RAID1+0 is not the best combination available. I would argue t= hat > > raid10,f2 is significantly better in a number of areas. >=20 > I'd guess Linux software RAID would be lucky to have 1% of RAID deplo= yments > worldwide--very lucky. The other 99%+ are HBA RAID or SAN/NAS "appli= ances" most > often using custom embedded RTOS with the RAID code written in assemb= ler, > especially in the case of the HBAs. For everything not Linux mdraid,= RAID 10 > (aka 1+0) is king of the hill, and has been for 15 years+ Yes, you are right, Linux MD really has an advantage here:-) > >> Something smells bad here. Does one of the RAID companies own a p= atent or > >> trademark on "RAID 10"? I'll look into this. It just doesn't mak= e any sense > >> for RAID 10 to be omitted from the SNIA DDF but to be referenced i= n the manner > >> it is. > >=20 > > It looks like they do define all major basic RAID disk layouts. (ex= cept > > raid10,f2 of cause) . RAID1+0 is a derived format, maybe that is ou= t of > > scope of the DDF standard. >=20 > "A secondary virtual disk is a VD configured using hybrid RAID levels= like > RAID10 or RAID50. Its elements are BVDs." >=20 > So apparently their Disk Data Format specification doesn't include hy= brid RAID > levels. This makes sense, as the _on disk_ layout of RAID 10 is iden= tical to > RAID 1. Yes, raid10 is just a variation of RAID1, actually raid10,n2 is identical on the disk to RAID1, eg for a 2 drive or 4-drive array. > We apparently need to be looking for other SNIA documents to find the= ir > definition of RAID 10. That is what started us down this tunnel isn'= t it? > We're so deep now there's no light and I can't see the path behind me= anymore. ;) I dont think SNIA defines RAID 10, which is a specific Linux MD thing. =46or RAID1+0, I think it is covered by the DDF standard, as what DDF i= s aimed at is defining formats on the disks to portably handle RAID. That means that you can move a set of disks used in one manufacturer's=20 configuration to another make's configuration, and it will still work= =2E And it will also work with RAID1+0, as the underlying RAID1 and RAID0 formats are defined in DDF. So no need to add specific RAID1+0 definitions. Also RAID1 may mean different layouts, like the "far" and "offset" layouts, and it would mean an explosion of definitions of RAID1+0 if you should name and standardize all of these variations of RAID1+0 explicitely. best regards keld -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html