Revision - 8ed3a19 - md: don't attempt read-balancing for raid10 'far' layouts - origin: https://github.com/torvalds/linux

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Revision 8ed3a19563b6c05b7625649b1769ddb063d53253 authored by Keld Simonsen on 04 March 2008, 22:29:34 UTC, committed by Linus Torvalds on 05 March 2008, 00:35:18 UTC

md: don't attempt read-balancing for raid10 'far' layouts

This patch changes the disk to be read for layout "far > 1" to always be the
disk with the lowest block address.

Thus the chunks to be read will always be (for a fully functioning array) from
the first band of stripes, and the raid will then work as a raid0 consisting
of the first band of stripes.

Some advantages:

The fastest part which is the outer sectors of the disks involved will be
used.  The outer blocks of a disk may be as much as 100 % faster than the
inner blocks.

Average seek time will be smaller, as seeks will always be confined to the
first part of the disks.

Mixed disks with different performance characteristics will work better, as
they will work as raid0, the sequential read rate will be number of disks
involved times the IO rate of the slowest disk.

If a disk is malfunctioning, the first disk which is working, and has the
lowest block address for the logical block will be used.

Signed-off-by: Keld Simonsen <keld@dkuug.dk>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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Tip revision: 8ed3a19563b6c05b7625649b1769ddb063d53253 authored by Keld Simonsen on 04 March 2008, 22:29:34 UTC
md: don't attempt read-balancing for raid10 'far' layouts

Tip revision: 8ed3a19

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lib
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.gitignore	-rw-r--r--	644 bytes
.mailmap	-rw-r--r--	3.6 KB
COPYING	-rw-r--r--	18.3 KB
CREDITS	-rw-r--r--	90.4 KB
Kbuild	-rw-r--r--	1.6 KB
MAINTAINERS	-rw-r--r--	95.1 KB
Makefile	-rw-r--r--	52.8 KB
README	-rw-r--r--	16.5 KB
REPORTING-BUGS	-rw-r--r--	3.1 KB

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md: don't attempt read-balancing for raid10 'far' layouts

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