Yes and no. If you have 2 drives and you add one more, we can make it do all new chunks over 3 drives. But, turning the existing double mirror chunks into a triple mirror requires a balance. -chris On Wed, Jun 20, 2012 at 07:34:27PM -0600, H. Peter Anvin wrote: > Could you have a mode, though, where M = N at all times, so a user doesn't end up adding a new drive and get a nasty surprise? > > Chris Mason <chris.mason@xxxxxxxxxxxx> wrote: > > >On Wed, Jun 20, 2012 at 06:35:30PM -0600, Marios Titas wrote: > >> On Wed, Jun 20, 2012 at 12:27 PM, H. Peter Anvin <hpa@xxxxxxxxx> > >wrote: > >> > Yet another boot loader support request. > >> > > >> > Right now btrfs' definition of "RAID-1" with more than two devices > >is a > >> > bit unorthodox: it stores on any two drives. "True RAID-1" would > >> > instead store N copies on each of N devices, the same way an actual > >> > RAID-1 would operate with an arbitrary number of devices. > >> > > >> > This means that a bootloader can consider a single device in > >isolation: > >> > if the firmware gives access only to a single device, it can be > >booted. > >> > Since /boot is usually a very small amount of data, this is a very > >> > reasonable tradeoff. > >> > >> +1 > >> > >> In fact, the current RAID-1 should not have been called RAID-1 at > >all, > >> it is confusing. > > > >With the raid5/6 code, I'm changing raid1 (and raid10) to have a > >configurable number of copies. So, you'll be able to have N copies on > >M > >drives, where N <= M. > > > >-chris > > -- > Sent from my mobile phone. Please excuse brevity and lack of formatting. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
