Re: new superblock and raid10 support in mdadm

From: Neil Brown <redacted>
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
-- 
If you hear muffled screams, consider it a request for beam out.
	Tom Paris in Voyager
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