Re: Prepping to install: a digression

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Tue, 30 Jun 2015 08:34:29 -0453
    From:        "William A. Mahaffey III" <wam%hiwaay.net@localhost>
    Message-ID:  <5592996E.50208%hiwaay.net@localhost>

  | I am seeking highest storage density/usage with more reliability than 
  | RAID0, so RAID5 (or possibly RAID0 w/ another machine backing up) looks 
  | like the best option.

For max space, with redundancy, it (raid5) is - and performance is adequate
(I certainly use it, or have in the past and will again) - especially where
the data is read mostly, which is common for most data, and where N (the number
of drives in the raid set) is 2^M + 1 (and M is an integer > 0), and even
better, where the stripe size matches the filesystem data block size.

To be clear, for a raid5 set with N drives (not counting spares) you
get data on N-1 and parity on the other one ... but that doesn't mean
that there is one specific drive dedicated to parity, which of the N
drives holds the parity varies from slice to slice (inside the raid array,
these slices have nothing whatever to do with MBR or GPT partitions that some
other OS's refer to as slices).    So, all drives with have (N-1)/N (* 100) %
of their capacity used for data, and 1/N (* 100) % of their capacity used
for parity.

kre