i think that partial failure (raid0 fail) of a mirror, is a fail (since all mirror is repaired and resync) the security is, if you lose all mirrors you have a device so your 'secure' is the number of mirrors, not the number of disks ssd or another type of device... how many mirrors you have here: raid0= 1,2(a) 3,4(b) raid1=a,b 1 mirror (a or b) and here: raid1=1,2(a) 3,4(b) raid0=ab 1 mirror (a or b) let´s think about hard disk? your hard disk have 2 disks? why not make two partition? first partition is disk1, second partition is disk2 mirror it what´s your security? 1 mirror is it security? normaly when a harddisk crash all disks inside it crash but you is secury if only one internal disk fail... that´s the point, how many mirror? the point is with raid1+0 (raid10) we know that disks are fragments (raid1) with raid0+1 we know that disks are a big disk (raid0) the point is, we can´t allow that information stop, we need mirror to be secured (1 is good, 2 better, 3 really better, 4 5 6 7...) you can´t break mirror (not disk) to don´t break mirror have a second mirror (raid0 don´t help here! just raid1) with raid10 you will repair smal size of information (raid1), here sync will cost less time with raid01 you will repair big size of information (raid0), here sync will cost more time 2011/1/31 Denis <denismpa@xxxxxxxxx>: > 2011/1/31 Roberto Spadim <roberto@xxxxxxxxxxxxx>: >> hum that's right, >> but not 'increase' (only if you compare raid0+1 betwen raid1+0) using >> raid1 and after raid0 have LESS point of fail between raid 0 and after >> raid 1, since the number of point of fail is proportional to number of >> raid1 devices. > In that case, in an occurency of a failury, you will take much longer > to rebuild the failed disk, at least, double the time. > > >> >> 2011/1/31 Robin Hill <robin@xxxxxxxxxxxxxxx>: >>> On Mon Jan 31, 2011 at 01:00:13PM -0200, Roberto Spadim wrote: >>> >>>> i think make two very big raid 0 >>>> and after raid1 >>>> is better >>>> >>> Not really - you increase the failure risk doing this. With this setup, >>> a single drive failure from each RAID0 array will lose you the entire >>> array. With the reverse (RAID0 over RAID1) then you require both drives >>> in the RAID1 to fail in order to lose the array. Of course, with a 4 >>> drive array then the risk is the same (33% with 2 drive failures) but >>> with a 6 drive array it changes to 60% for RAID1 over RAID0 versus 20% >>> for RAID0 over RAID1. >>> >>> Cheers, >>> Robin >>> -- >>> 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 >> > > > > -- > 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
