Re: Prepping to install: a digression

["William A. Mahaffey III" <wam%hiwaay.net@localhost>]

On 06/30/15 04:31, Robert Elz wrote:
>      Date:        Mon, 29 Jun 2015 22:54:19 -0453
>      From:        "William A. Mahaffey III" <wam%hiwaay.net@localhost>
>      Message-ID:  <55921174.3020101%hiwaay.net@localhost>
>
>    | Which is right, the list & I or those lying man pages ?
>
> The list, and the man pages, both say the same thing as I recall.
>
> For any stripe on the raid, N-1 drives hold the data, and one drive
> holds the parity.
>
> Whether the same drive holds all the parity. or whether it is spread
> around the drives was soething I said I wasn't sure about (in a previous
> message on the list - relating to NetBSD's implementation).

To be clear, I *wasn't* casting aspersions, just trying to be flip, 
sorry for any offense !!!

> But why do you care?   Unless you're planning on working on the raidframe
> implementation, the only thing it affects is performance.   (Spreading the
> parity around allows all drives to participate in normal read operations,
> and the extra writes on write ops to be spread around all of the drives,
> instead of leaving the parity drive idle on read ops, and a bottleneck on
> writes).
>
> Aside from that (and if you are seeking truly high performance, raid5 is not
> the solution) it makes no difference at all to anything that you do, or
> observe.
>
> kre


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. RAID10 would probably be more reliable, but 1/2 
storage usage. With only 6 drives, or more accurately slices, I want as 
many active as possible. RAID5 would have 4 active (w/ 1 spare, 1 
parity) & some fault tolerance, RAID0 would have all 6 active, but no 
fault tolerance.

--

	William A. Mahaffey III

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