it´s not just a probability problem, it´s a probability based on variable type if you want probability based on mirror you have a result, if you want probability based on disk you have another result raid0 allow disks (but we don´t have a 0,5 raid0 system, we just allow integers numbers, we can´t allow decimal numbers on this probability!) the problem here is: raid0 isn´t divisible, we can´t run a 0,5 raid0 system. we need a full working raid0 to have a working mirror, a half disk don´t help us to WORK, just to test and play with data, not to real production work! why we don´t buy disks with bad blocks? got the problem? for tests ok, for production NEVER i had a raid1 system broken last month, i have luck, two disks of 4 disks are broken, the first raid0 and the last raid0 but they are on separated mirrors (the server hit the floor, sorry boss =( ). i lost information? no! the last raid0 brolen disk was never used =], i used concatenate raid0 (LINEAR), if i was using raid0 with stripe i was f**** result: 4 new disks, 2 working 2 broken (i opened it! and 2 was good, after open it they are broken hehehe) that´s the problem, we can´t allow luck on production servers, consider using probability based on mirrors(only integer numbers) not on disks(decimal number of mirror) i could lost all my informations since i broken two mirrors on two mirror based server... make probability using integers not decimal numbers... since raid1 is mirrors based another example... i want raid10 (2mirrors) if i make partition on 4 disks (8 partitions, 2 per disk) and make raid1 on each partition on same disk (4 disk self mirrored) what the probability? i tell you is it mirror based or disk based? since software raid (mdadm) is mirror based you have 2 mirrors, you can lost 1 mirror! that´s the key. for mdadm you can´t go inside mirror device (just for raid0) but you can´t tell that´s a good probability look OCZ Revo-drive it´s a ssd pci board with two SATA SSD storage (120gb revodrive = 2x 55gb ssd) if i make self mirror i have a fault tolerant system? yes! understand now? for mdadm we have 2 mirrors, don´t make probability based on disks! make probability based on mirrors! 2011/1/31 Denis <denismpa@xxxxxxxxx>: > 2011/1/31 Phillip Susi <psusi@xxxxxxxxxx>: >> On 1/31/2011 2:53 PM, Roberto Spadim wrote: >>> if you have a bigger and bigger and bigger disk configuration and only >>> two mirrors you still with 50% > might help http://en.wikipedia.org/wiki/Probability > > > -- > Denis Anjos, > www.versatushpc.com.br > -- > 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
