if you go to hardware level, check first.. is your server mirror based? if you lost your UPS what´s the total system security? here (mdadm) we just use mdadm, we don´t need probability for upper layers (filesystem) or bottom layers (hardware) we need probability on devices that´s the layer that mdadm work, linux devices. that´s why we should use mirror based probability! not disk based! 2011/1/31 Roberto Spadim <roberto@xxxxxxxxxxxxx>: > 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 > -- 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
