On Sun, 14 Mar 2010 00:31:01 +0300
"Majed B." [off-list ref] wrote:

Neil,

Since when was this possible? I always thought that it had to have an
even number of disks.

md has never imposed a 2-drive restriction on raid1.  That would be fairly
pointless.

Requiring an even number of devices would also be pointless.

The term "mirror" is possibly a cause of confusion as it suggests an original
and a copy.  It also suggests that the copy is reflected in some way.
Neither of these are true.
RAID1 stores multiple copies of the same data.  All copies are equal.  You can
have as many or as few of them as you like.  1, 2, 3, 4, ....
NeilBrown

On Sun, Mar 14, 2010 at 12:26 AM, Neil Brown [off-list ref] wrote:

quoted

On Sat, 13 Mar 2010 16:06:38 -0500
Carlos Mennens [off-list ref] wrote:

quoted

I was told by my distributions Wiki page that Grub doesn't support
RAID 5 or RAID 6 so I would need to create a volume with three disks
and set the level to RAID 1:

# mdadm --create /dev/md1 --level=1 --raid-devices=3 /dev/sda1
/dev/sdb1 /dev/sdc1 --spare-devices=1 /dev/sdd1

Is this possible to mirror three identical drive partitions? I was
talking to some co-workers and was told that I could only pair two
drives on RAID 1.

Your co-workers are wrong, at least for md raid.  With md, a RAID1 can have
any number of devices from 1 upwards - the limit varies in different
situations but is at least 28.

Try it and see.

NeilBrown

quoted

Can anyone please help me understand this?
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