2011/1/31 Roberto Spadim <roberto@xxxxxxxxxxxxx>: > no matter what raid1 or raid10 system we use > raid1 is mirror! letÂs think that raid0 = more than one disk (not a > single disk)... > > if a hard disk inside a mirror (raid1) fail (it can be a raid0 or a > single disk) the mirror is failed > for example: thereÂs no 25% survival for 2 mirrors with 4 disks! > probability, here, is mirror based, not disk based! > itÂs not a question about linux implementation is a question for > generic raid1 (mirror) system (1 failed 2 mirrors = 1 mirror failed > but 1 mirror working) > > you only can have 25% 'survival' if you can use 4 disks, or multiples > of 4, for raid1 > if your raid0 is broken you donÂt have a raid0! you have a broken raid > = broken mirror (for raid1)! > > should i write it again? for raid10 (raid1+0) with 4 disks you can > only lost 1 disk! 1 disk lost = 1 raid0 lost = 1 mirror lost! > should i write it again? > > 2011/1/31 Keld JÃrn Simonsen <keld@xxxxxxxxxx>: >> On Mon, Jan 31, 2011 at 02:17:37PM -0600, Stan Hoeppner wrote: >>> Keld JÃrn Simonsen put forth on 1/31/2011 1:28 PM: >>> > Top-posting... >>> > >>> > How is the raid0+1 problem of only 33 % survival for 2 disk with RAID10? >>> > >>> > I know for RAID10,F2 the implementation in Linux MD is bad. >>> > It is only 33 % survival, while it with a probably minor fix could be 66%. >>> > >>> > But how with RAID10,n2 and RAID10,o2? >>> >>> I don't care what Neil or anyone says, these "layouts" are _NOT_ RAID 10. ÂIf >>> you want to discuss RAID 10, please leave these non-standard Frankenstein >>> "layouts" out of the discussion. ÂIncluding them only muddies things unnecessarily. >> >> Please keep terminology clean, and non-ambigeous. >> Please refer to the old term RAID10 as RAID1+0, which is also the >> original and more precise term for that concept of multilevel RAID. >> >> RAID10 on this list refers to the RAID10 modules of the Linux kernel. >> >> I can concurr that this may be a somewhat misleading term, as it is >> easily confused with the popular understanding of RAID10, meaning >> RAID1+0. And I see Linux RAID10 as a family of RAID1 layouts. >> Indeed RAID10,n2 is almost the same as normal RAID1, and RAID10,o2 >> is an implementation of a specific layout of the RAID1 standard. >> RAID10,f2 could easily also be seen as a specific RAID1 layout. >> >> But that is the naming of terms that we have to deal with on this Linux >> kernel list for the RAID modules. >> >> 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 Âhttp://vger.kernel.org/majordomo-info.html >> > > > > -- > Roberto Spadim > Spadim Technology / SPAEmpresarial > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at Âhttp://vger.kernel.org/majordomo-info.html > In a 4 disk RAID1+0 (where you have 2 HDDs in RAID1 (a) and 2 other HDDs in RAID1 (b), then put them together in a RAID0) you can lose a maximum of 2 HDDs, without any data loss. Sure, the "mirror" is "broken", but your data is intact. So, you can actually rip out 2 HDDs and still have your data, providing you pull the "right" drives. A single disk can be described as RAID0 (as it's not redundant). // Mathias -- 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
