Re: [PATCH 0/5] [RFC] RAID-level terminology change

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On 09/03/13 20:31, Hugo Mills wrote:
>    Some time ago, and occasionally since, we've discussed altering the
> "RAID-n" terminology to change it to an "nCmSpP" format, where n is the
> number of copies, m is the number of (data) devices in a stripe per copy,
> and p is the number of parity devices in a stripe.
> 
>    The current kernel implementation uses as many devices as it can in the
> striped modes (RAID-0, -10, -5, -6), and in this implementation, that is
> written as "mS" (with a literal "m"). The mS and pP sections are omitted
> if the value is 1S or 0P.
> 
>    The magic look-up table for old-style / new-style is:
> 
> single 		 1C (or omitted, in btrfs fi df output)
> RAID-0		 1CmS
> RAID-1		 2C
> DUP			 2CD
> RAID-10		 2CmS
> RAID-5		 1CmS1P
> RAID-6		 1CmS2P

Are these the only valid options? Are 'sensible' new levels (eg 3C, mirrored to 3 disk or 1CmS3P, like raid6 with but with 3 parity blocks) allowed? Are any arbitrary levels allowed (some other comments in the thread suggest no)? Will there be a recommended (or supported) set?



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