Re: RAID1 On 3 Drives

["Majed B." <majedb@gmail.com>]

Thank you Neil for the valuable clarification :)

On Sun, Mar 14, 2010 at 12:50 AM, Neil Brown <neilb@suse.de> wrote:
> On Sun, 14 Mar 2010 00:31:01 +0300
> "Majed B." <majedb@gmail.com> 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 <neilb@suse.de> wrote:
>> > On Sat, 13 Mar 2010 16:06:38 -0500
>> > Carlos Mennens <carloswill@gmail.com> wrote:
>> >
>> >> 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
>> >
>> >>
>> >> Can anyone please help me understand this?
>> >> --
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>>
>>
>>
>
>



-- 
       Majed B.
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