Re: new superblock and raid10 support in mdadm

[Jurriaan <thunder7@xs4all.nl>]

From: Neil Brown <neilb@cse.unsw.edu.au>
Date: Tue, Sep 14, 2004 at 11:08:53AM +1000
> A new format is being supported because the old format has problems.
> One is that it cannot work with devices larger than 2 Gigabytes (and I
> have had a request from someone who wanted to include such a device in
> an MD array).

I presume you mean terabyte, but I'm not sure you don't mean petabyte or
something else very large?

> The raid10 module is in 2.4.9-rc2 and will be in 2.4.9 when it gets
> released. 

2.6.9 I presume?

> /*
>  * RAID10 provides a combination of RAID0 and RAID1 functionality.
>  * The layout of data is defined by
>  *    chunk_size
>  *    raid_disks
>  *    near_copies (stored in low byte of layout)
>  *    far_copies (stored in second byte of layout)
>  *
>  * The data to be stored is divided into chunks using chunksize.
>  * Each device is divided into far_copies sections.
>  * In each section, chunks are laid out in a style similar to raid0, but
>  * near_copies copies of each chunk is stored (each on a different drive).
>  * The starting device for each section is offset near_copies from the starting
>  * device of the previous section.
>  * Thus there are (near_copies*far_copies) of each chunk, and each is on a different
>  * drive.
>  * near_copies and far_copies must be at least one, and there product is at most

----------------------------------------------------------their

>  * raid_disks.
>  */

Good luck,
Jurriaan
-- 
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