On Sun, Mar 10, 2013 at 12:23:56PM +0100, Martin Steigerwald wrote: > Hi Hugo, > > Am Samstag, 9. März 2013 schrieb Hugo Mills: > > 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 > > What does the "D" in "2CD" mean? Its not explained above, unless I miss > something.
Oh, sorry. It's "reduced redundancy", aka DUP -- i.e. you get that number of copies, but not guarantee that the copies all live on different devices. I'm not devoted to showing it this way. Other suggestions for making this distinction are welcomed. :) > > RAID-10 2CmS > > RAID-5 1CmS1P > > RAID-6 1CmS2P > > I think its great to clarify the RAID-level terminology, but I find the new > notation a bit, hmmm, cryptic. > > Maybe for displaying it would be nice to show a more verbose format like > > 2 copies, many stripes, 1 parity (1CmS1P) > > by default and the abbreviated one in parentheses? The only place it gets output right now is btrfs fi df, and something that verbose would probably get in the way. > Any other idea to make it less cryptic? Not necessarily less cryptic, but using lower-case c/s/p would probably improve readability: 1c2s1p. Possibly also using * instead of m for the "s" setting: 2c*s. That will change the heights of the characters, so you only really need to look at the tall ones. Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- There's many a slip 'twixt wicket-keeper and gully. ---
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