nice, english isn´t my language, i´m not offended, i know that we have problem reading my words... thanks =) probability using ´raid world words´, isn´t ´mdadm world words´ since mdadm don´t work with disk or ssd (it work with devices) probability can´t go inside device to try to explain anything without knowing how mdadm works if you want global system probability, don´t call mdadm as a source of probability if you don´t know what it can do. can a failed mirror be used without sync? no another point, after a fail (disk) will your system stop or continue? did you probability consider a fixed point in time or a global scenario? talking about probability, try to explain the context, and how to calculate it (it´s necessary, belive me) using mdadm raid10 how many devices could you lose, for mirror context? 1 mirror, right? losing 1 mirror = losing 1 raid0 disk, right? if ok, make probability (for mdadm world) with this mirrors, not with disks use probability with the most secure results, it´s not a academic probability, it´s a production use software, use secure results. the original question... how could i make probability about security for mdadm software? raid1 raid10 raid 5 raid6 raid0, all raid, maybe the answer could be documentated on raid wiki =), just to don´t get back again in this mail list anyone could help with this part of documentation probability isn´t just numbers, it´s numbers+context a car can be a vehicle, but a vehicle can be a truck too probability numbers are nothing without context 2011/2/1 Jon Nelson <jnelson-linux-raid@xxxxxxxxxxx>: > On Tue, Feb 1, 2011 at 4:01 AM, David Brown <david@xxxxxxxxxxxxxxx> wrote: >> On 31/01/2011 23:52, Keld Jørn Simonsen wrote: >>> >>> raid1+0 and Linux MD raid10 are similar, but significantly different >>> in a number of ways. Linux MD raid10 can run on only 2 drives. >>> Linux raid10,f2 has almost RAID0 striping performance in sequential read. >>> You can have an odd number of drives in raid10. >>> And you can have as many copies as you like in raid10, >>> >> >> You can make raid10,f2 functionality from raid1+0 by using partitions. For >> example, to get a raid10,f2 equivalent on two drives, partition them into >> equal halves. Then make md0 a raid1 mirror of sda1 and sdb2, and md1 a >> raid1 mirror of sdb1 and sda2. Finally, make md2 a raid0 stripe set of md0 >> and md1. >> >> If you have three disks, you can do that too: >> >> md0 = raid1(sda1, sdb2) >> md1 = raid1(sdb1, sdc2) >> md2 = raid1(sdc1, sda2) >> md3 = raid0(md0, md1, md2) >> >> As far as I can figure out, the performance should be pretty much the same >> (although wrapping everything in a single raid10,f2 is more convenient). > > The performance will not be the same because. Whenever possible, md > reads from the outermost portion of the disk -- theoretically the > fastest portion of the disk (by 2 or 3 times as much as the inner > tracks) -- and in this way raid10,f2 can actually be faster than > raid0. > > > -- > Jon > -- > 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 > -- 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 http://vger.kernel.org/majordomo-info.html
