From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ravi Pinjala Subject: Re: Raid1 with 3 drives Date: Fri, 05 Mar 2010 19:02:35 -0600 Message-ID: <4B91A9AB.1020005@p-static.net> References: <013A5A0F-6BB8-4CF0-855F-0A80BEA8B1CC@adtran.com> <20100305194047.GA15771@localhost.localdomain> <20100305203148.GB15771@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linux-btrfs@vger.kernel.org To: Bart Noordervliet Return-path: In-Reply-To: List-ID: On 03/05/10 15:49, Bart Noordervliet wrote: > On Fri, Mar 5, 2010 at 21:31, Josef Bacik wrote: >>> Since I have three devices in a RAID1 pool, can it survive 2 drive failures? >> >> Yes, tho you won't be able to remove more than 1 at a time (since it wants you >> to keep at least two disks around). Thanks, >> >> Josef > > Hmm, I would expect the raid1 data mode to keep 2 copies of each file > and thus yield 50% effective storage capacity, even with 3 disks. I > see no real reason to stick with the full-disk mirroring mentality of > previous raid systems since raid implemented in a filesystem works > differently. Or would it be difficult to implement btrfs raid1 like > this? > > Maybe it's worth to consider leaving the burdened raid* terminology > behind and name the btrfs redundancy modes more clearly by what they > do. For instance "-d double|triple" or "-d 2n|3n". And for raid5/6 "-d > single-parity|double-parity" or "-d n+1|n+2". > > Regards, > > Bart > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > This would be pretty excellent - there's a real need for a storage system where you can just give it a bunch of disks and a policy, and let the system worry about the details. Current RAID implementations are pretty inflexible, for example when dealing with disks of varying size. --Ravi