On Tuesday, January 15, 2013 11:07:17 am Allen Landsidel wrote: > > http://www.freebsd.org/cgi/query-pr.cgi?pr=166589&cat= > > Can somebody else talk some sense into this guy? I'm losing my temper.
Well, is his last question correct? If the RAID BIOS writes the metadata the same way regardless, then is there a reason (beyond "pure correctness") to not just treat RAID0+1 as RAID10? > -------- Original Message -------- > Subject: Re: bin/166589: atacontrol(8) incorrectly treats RAID10 and > 0+1 the same > Date: Tue, 15 Jan 2013 17:55:57 +0200 > From: Alexander Motin <m...@freebsd.org> > To: Allen Landsidel <landsidel.al...@gmail.com> > CC: bug-follo...@freebsd.org > > > > Their on-disk formats are identical. Even if RAID BIOS supports RAID0+1, > there is no problem to handle it as RAID10 at the OS level. That gives > better reliability without any downsides. I think there is much higher > chance that inexperienced user will choose RAID0+1 by mistake, then > experienced wish do to it on intentionally. Do you know any reason why > RAID0+1 can't be handled as RAID10? > > On 15.01.2013 17:28, Allen Landsidel wrote: > > Most devices typically only support one level or the other, but not > > both. I don't "Insist that it should exist", it *does* exist. Both > > levels do, and they are not the same thing. > > > > As for why it should be "available" to the user, I think that's a pretty > > silly question. If their hardware supports one or both levels, they > > should be available to the user -- and called by their correct names. > > > > On 1/15/2013 03:12, Alexander Motin wrote: > >> That is clear and I had guess you mean it, but why do you insist that > >> such RAID0+1 variant should even exist if it has no benefits over > >> RAID10, and why it should be explicitly available to user? > >> > >> On 15.01.2013 04:51, Allen Landsidel wrote: > >>> They are not variants in terminology, they are different raid levels. > >>> Raid0+1 is two RAID-0 arrays, mirrored into a RAID-1. if one of the > >>> disks fails, that entire RAID-0 is offline and must be rebuilt, and all > >>> redundancy is lost. A RAID-10 is composed of N raid-1 disks combined > >>> into a RAID-0. If one disk fails, only that particular RAID-1 is > >>> degraded, and the redundancy of the others is maintained. > >>> > >>> 0+1 cannot survive two failed disks no matter how many are in the > >>> array. 10 can survive half the disks failing, if it's the right half. > >>> > >>> This is something people who've never used more than 4 disks fail to > >>> grasp, but those of us with 6 (or many many more) know very well. > >>> > >>> On 1/14/2013 21:46, Alexander Motin wrote: > >>>> There could be variants in terminology, but in fact for most of users > >>>> they are the same. If you have opinion why they should be treated > >>>> differently, please explain it. > > > > > -- > Alexander Motin > > > > _______________________________________________ > freebsd-hardware@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hardware > To unsubscribe, send any mail to "freebsd-hardware-unsubscr...@freebsd.org" > -- John Baldwin _______________________________________________ freebsd-hardware@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hardware To unsubscribe, send any mail to "freebsd-hardware-unsubscr...@freebsd.org"
