On Thu, Feb 12, 2009 at 09:52:32PM +1100, NeilBrown wrote: > On Thu, February 12, 2009 8:46 pm, Keld Jørn Simonsen wrote: > > On Thu, Feb 12, 2009 at 09:13:17AM +0000, Steve Fairbairn wrote: > >> Keld Jørn Simonsen wrote: > >> > > >> >I would rather have functionality to convert raid10 to raid5. > >> >raid1 should be depreciated, as raid10,n2 for all purposes is the same > >> >but better implementation and performance, and raid10,f2 and raid10,o2 > >> >are even better. Nobody should use raid1 anymore. > >> > > >> Complete ignorance of raid10 here, but is raid10,<anything> bootable, > >> like raid1 is? I use raid1 on my root and boot partitions. > > > > AFAIK, raid10,n2 in default mode (superblock etc) is bootable, as it > > looks like two copies of a normal FS. I think this was even reported > > on this list at some time. > > > > You are not the only one that does not know much about raid10. I think > > most Linux administrators don't. And other system adminstrators most > > likely don't either. > > > > Maybe we should rename raid10 to raid1? > > > > Raid10 should just be an enhanced raid1. And I understand from Neil that > > raid10,o2 is mostly done because it is a standard raid1 layout. So it is > > strange that it is not available with raid1 in Linux. And I also think > > that the raid10,f2 layout is available from some HW raid controllers, as > > their implementation of raid1. So all what is in raid10 is other places > > considered raid1 stuff. > > > > The 'offset' layout came about to be able to support a DDF format > which is called: > > 4.2.18 Integrated Offset Stripe Mirroring (PRL=11, RLQ=01) > > (4.2.18 is the section of the document > PRL is Primary Raid Level > RLQ is Rail Level Qualifier > ) > There is also > > 4.2.17 Integrated Adjacent Stripe Mirroring (PRL= 11, RLQ=00) > > which is essentially the same as our n2 layout. > > You should see their > 4.3.4 Spanned Secondary RAID Level (SRL=03) > > Though. That would be really .. interesting to implement. > > > You can down load the ddf spec at > > http://www.snia.org/tech_activities/standards/curr_standards/ddf/ > > NeilBrown I did look at the spec, and I could not find something that looked like f2. I then sent them a mail suggesting standardizing raid10,f2 - some months ago. No answer (yet...) Am I right that raid10,f2 is not described in their spec? A bit odd. The idea behind raid10,f2 is quite straightforward, and gives good results. 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
