[Discuss] btrfs

[Derek Atkins]

Rich Pieri <richard.pieri at gmail.com> writes:

> On Fri, 22 Feb 2013 11:29:42 -0500
> Jerry Feldman <gaf at blu.org> wrote:
>
>> So, assume I have 2 physical volumes, /dev/sda and /dev/sdb.
>> mkfs.btrfs -d raid1 /dev/sda /dev/sdb
>> What happens if I get a failure on /dev/sdb.
>> Assume no snapshots.
>
> "-d raid1" means mirrored data. Metadata is mirrored by default even
> on single drive volumes.
>
> If /dev/sdb faults then you should lose no data since every extent is
> replicated on both /dev/sda and /dev/sdb. If a bit error arises on
> either sda or sdb then a scrub will detect the error and it should
> automatically correct it using the replica on the other device.

I'm sure these are silly questions I could google myself, but: what
happens with more than 2 devices?  For example, if I used:

  mkfs.btrfs -d raid1 /dev/sda /dev/sdb /dev/sdc /dev/sdd

It this going to be more like raid10?

Also, can you add new devices "later" to an existing FS?  E.g., let's
say we start with 2 devices (sda, sdb) -- can I later add more devices?

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available