From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Majed B." Subject: Re: RAID1 On 3 Drives Date: Sun, 14 Mar 2010 06:30:35 +0300 Message-ID: <70ed7c3e1003131930ucd1898vae8edc49ece03740@mail.gmail.com> References: <20100314082649.187dae9a@notabene.brown> <70ed7c3e1003131331g14e30331k8b97520c906431fd@mail.gmail.com> <20100314085056.5ea95f95@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20100314085056.5ea95f95@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: LinuxRaid List-Id: linux-raid.ids Thank you Neil for the valuable clarification :) On Sun, Mar 14, 2010 at 12:50 AM, Neil Brown wrote: > On Sun, 14 Mar 2010 00:31:01 +0300 > "Majed B." wrote: > >> Neil, >> >> Since when was this possible? I always thought that it had to have a= n >> even number of disks. > > md has never imposed a 2-drive restriction on raid1. =C2=A0That 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. =C2=A0It also suggests that the copy is reflected in some= way. > Neither of these are true. > RAID1 stores multiple copies of the same data. =C2=A0All copies are e= qual. =C2=A0You can > have as many or as few of them as you like. =C2=A01, 2, 3, 4, .... > NeilBrown > > >> >> 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 suppor= t >> >> RAID 5 or RAID 6 so I would need to create a volume with three di= sks >> >> and set the level to RAID 1: >> >> >> >> # mdadm --create /dev/md1 --level=3D1 --raid-devices=3D3 /dev/sda= 1 >> >> /dev/sdb1 /dev/sdc1 --spare-devices=3D1 /dev/sdd1 >> >> >> >> Is this possible to mirror three identical drive partitions? I wa= s >> >> talking to some co-workers and was told that I could only pair tw= o >> >> drives on RAID 1. >> > >> > Your co-workers are wrong, at least for md raid. =C2=A0With md, a = RAID1 can have >> > any number of devices from 1 upwards - the limit varies in differe= nt >> > 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-r= aid" in >> >> the body of a message to majordomo@vger.kernel.org >> >> More majordomo info at =C2=A0http://vger.kernel.org/majordomo-inf= o.html >> > >> > -- >> > 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 >> > >> >> >> > > --=20 Majed B. -- 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