Date: Fri, 12 Jun 2015 09:12:54 -0453
From: "William A. Mahaffey III" <wam%hiwaay.net@localhost>
Message-ID: <557AE76F.7090701%hiwaay.net@localhost>
| So, the question is: Do I indeed have
| to specify a spare drive explicitly in my raid.conf, or will raidctl
| intelligently decide to pick 1 & setup 'N-1' active devices for 'N'
| specified in the raid.conf file ?
You are confusing two different things, what you're thinking of as the "spare"
I think, is more correctly called the parity drive (and isn't actually
normally a physical drive, but is rotated around all the drives for different
slices of the raid - though I'm not sure if raidframe works that way).
Raid 5 needs N data drives + a parity drive to work - and to work effeciently,
N should be a power of two (like 2, or 4).
If a drive dies, data is reconstructed from the remaining N-1 drives, and
the parity (of course, when it is the parity that is dead, the data doesn't
need reconstructing).
A spare drive on the other hand is a completely unused drive, that just sits
around waiting for one of the other drives to die, at which point it replaces
that drive (automatically) and the raid continues to be fully operable
(allowing the dead drive to be replaced at leisure, and either become the
spare drive, or be reinserted into the raid set allowing the previously spare
drive to become spare again - which happens depends upon how the replacement
is inserted into the raid set).