On Mon, 9 May 2011 05:40:36 +0200 Keld Jørn Simonsen <keld@xxxxxxxxxx> wrote: > On Sun, May 08, 2011 at 05:25:24PM -0400, Miles Fidelman wrote: > > Luca Berra wrote: > > >On Fri, May 06, 2011 at 09:17:52AM +0200, Keld Jørn Simonsen wrote: > > >>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 > > >then we need rename the current raid1 functionality to 'mirror'. in > > >order to avoid further confusion. > > >besides, current raid10 does not support resizing, so the feature > > >should be added before ditching 'mirror' > > > > > > > The current md RAID1 does exactly what RAID1 is supposed to do. > > I changed my mind a little. > > I think we should follow SNIA wrt. RAID1 - all that SNIA would say is > RAID1 we also should be able to do as RAID1 - that would include > raid10-offset which directly was implemented in the Linux kernel > because of the SNIA RAID1 specification. It should also include raid10-far > in so far it is a raid1 type - say a raid10,f2 with only 2 disks. I think you misread SNIA-DDF. In DDF, arrays with a PRL (Primary RAID Level) of 1 can have an RLQ (RAID level qualifier) of 0 or 1. RLQ = 0 -> RAID1 with 2 devices RLQ = 1 -> RAID1 with 3 devices. DDF also devices a PRL of '11' which it calls "RAID-1E" (though this term only appears once in the DDFv1.2 spec) For PRL = 11 there are two options RLQ = 0 -> Integrated Adjacent Stripe Mirroring RLQ = 1 -> Integrated Offset Stripe Mirroring. These correspond to md/raid10 "near2" and "offset2". So DDF: RAID-1E corresponds to md: RAID-10 So an 'E' rather than a '0'. I would not be against allowing mdadm to accept "raid1e" as a synonym for 'raid10', and mentioning the alternate name in the documentation would be entirely appropriate. But RAID-1E is not RAID-1. Nor is RAID-10. > > Then we should keep the raid10 stuff. > > > The md RAID10 is a very specific, and unique approach that has > > similarities to, but is distinct from, RAID1+0, RAID0+1, RAID5, and RAID6. > > Yes, Linux MD raid10 is a very distinct type. We should talk with SNIA to get it > recognized. > > > What say we leave the names alone. Just beause one person is confused is > > no reason to further confuse things. > > The confusion is not just one person. The confusion is unbelievable common, > and has proven to be very hard to eliminate. If we align with the SNIA > standard, and further get the standard to align with us, then we should > have a chance in say 5 years to have reduced the confusion considerably. The world is full of confusion that is hard to eliminate. The problem here I think is simply people who do not educate themselves, either because they cannot be bothered, or because they cannot easily find the materials. The first is not really a fixable problem. The second we can address. Improve the already-good wiki or add more text to the man pages. Have an aim that every general-information question can be answered by simply posting a like or a passage from the man page. That would be really worthwhile. Changing names around is, I think, less valuable. Thanks, NeilBrown -- 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
