graid3

[nicodache]

Hello,

1. I don't see such a thing on the weblink you gave (acnc)
In my opinion, this rule is pure nonsense, as raid 3 just use a
separate drive to store stripe parity. You just need at least 3
drives, one for parity, 2 for data. you can do raid 3 with how many
drives you want.

2. because the raid controler/software thing can reconstruct the data
with only n-1 of the n drives in the array.
in random IO this can be quite usefull, while in sequential read, the
parity drive is not that much of use.

On Fri, Jul 25, 2008 at 11:46 AM, Wojciech Puchar
<wojtek at wojtek.tensor.gdynia.pl> wrote:
> i read the graid3 manual and http://www.acnc.com/04_01_03.html to make sure
> i know what's RAID3 and i don't understand few things.
>
> 1)
>
> "The number of components must be equal to 3, 5, 9, 17, etc.
>                (2^n + 1)."
>
> why it can't be say 5 disks+parity?
>
> 2) "-r  Use parity component for reading in round-robin fashion.
> "Without this option the parity component is not used at
> all for reading operations when the device is in a complete state.
>  With this option specified random I/O read operations are even 40% faster
> , but sequential reads are slower.  One cannot use this option if the -w
> option is also specified."
>
>
> how parity disk could speed up random I/O?
>
>
> is there any description of how graid3 actually works?
>
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