From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: RAID1 On 3 Drives Date: Sun, 14 Mar 2010 08:50:56 +1100 Message-ID: <20100314085056.5ea95f95@notabene.brown> References: <20100314082649.187dae9a@notabene.brown> <70ed7c3e1003131331g14e30331k8b97520c906431fd@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <70ed7c3e1003131331g14e30331k8b97520c906431fd@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: "Majed B." Cc: LinuxRaid List-Id: linux-raid.ids On Sun, 14 Mar 2010 00:31:01 +0300 "Majed B." wrote: > Neil, >=20 > 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 fai= rly pointless. Requiring an even number of devices would also be pointless. The term "mirror" is possibly a cause of confusion as it suggests an or= iginal 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 >=20 > On Sun, Mar 14, 2010 at 12:26 AM, Neil Brown wrote: > > On Sat, 13 Mar 2010 16:06:38 -0500 > > Carlos Mennens 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 dis= ks > >> and set the level to RAID 1: > >> > >> # mdadm --create /dev/md1 --level=3D1 --raid-devices=3D3 /dev/sda1 > >> /dev/sdb1 /dev/sdc1 --spare-devices=3D1 /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. =C2=A0With md, a R= AID1 can have > > any number of devices from 1 upwards - the limit varies in differen= t > > situations but is at least 28. > > > > Try it and see. > > > > NeilBrown > > > >> > >> Can anyone please help me understand this? > >> -- > >> To unsubscribe from this list: send the line "unsubscribe linux-ra= id" in > >> the body of a message to majordomo@vger.kernel.org > >> More majordomo info at =C2=A0http://vger.kernel.org/majordomo-info= =2Ehtml > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-rai= d" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at =C2=A0http://vger.kernel.org/majordomo-info.= html > > >=20 >=20 >=20 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html