18.07.2018 22:42, Goffredo Baroncelli пишет: > On 07/18/2018 09:20 AM, Duncan wrote: >> Goffredo Baroncelli posted on Wed, 18 Jul 2018 07:59:52 +0200 as >> excerpted: >> >>> On 07/17/2018 11:12 PM, Duncan wrote: >>>> Goffredo Baroncelli posted on Mon, 16 Jul 2018 20:29:46 +0200 as >>>> excerpted: >>>> >>>>> On 07/15/2018 04:37 PM, waxhead wrote: >>>> >>>>> Striping and mirroring/pairing are orthogonal properties; mirror and >>>>> parity are mutually exclusive. >>>> >>>> I can't agree. I don't know whether you meant that in the global >>>> sense, >>>> or purely in the btrfs context (which I suspect), but either way I >>>> can't agree. >>>> >>>> In the pure btrfs context, while striping and mirroring/pairing are >>>> orthogonal today, Hugo's whole point was that btrfs is theoretically >>>> flexible enough to allow both together and the feature may at some >>>> point be added, so it makes sense to have a layout notation format >>>> flexible enough to allow it as well. >>> >>> When I say orthogonal, It means that these can be combined: i.e. you can >>> have - striping (RAID0) >>> - parity (?) >>> - striping + parity (e.g. RAID5/6) >>> - mirroring (RAID1) >>> - mirroring + striping (RAID10) >>> >>> However you can't have mirroring+parity; this means that a notation >>> where both 'C' ( = number of copy) and 'P' ( = number of parities) is >>> too verbose. >> >> Yes, you can have mirroring+parity, conceptually it's simply raid5/6 on >> top of mirroring or mirroring on top of raid5/6, much as raid10 is >> conceptually just raid0 on top of raid1, and raid01 is conceptually raid1 >> on top of raid0. > And what about raid 615156156 (raid 6 on top of raid 1 on top of raid 5 on > top of....) ??? > > Seriously, of course you can combine a lot of different profile; however the > only ones that make sense are the ones above.
RAID50 (striping across RAID5) is common. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
