You are not logged in.
I'm using btrfs-raid1 on two 2.0 TiB disks for my multimedia archive. Now I'd like to enlarge it using two unused 1.0TiB disks lying around.
Reading the btrfs-wiki at kernel.org I see there is currently no way changing the raid level from 1 to 10 and then adding the two new disks, so I must either create a second raid1-pair with separate mount point or stick with raid1.
Now comes the confusion, quoting a post on the btrfs mailing-list:
(...) By contrast, btrfs' so-called raid1 is actually only two-way mirroring,
regardless of the number of devices, a VERY critical difference if the
intent was to actually allow three of the four devices to die and still
have access to the data on the fourth one, as a true raid1 would give you
but btrfs' so-called raid1 will NOT. However, btrfs WOULD take advantage
of the full size of the devices (barring bugs, remember btrfs is still
experimental/development/testing-only in the mainstream kernel at least),
giving you access to the full (1.5*2+0.5*2)/2=2T of space. (...)
So btrfs-raid1 always mirrors two-way, regardless of the number of disks? Didn't know that. The post even mentions my four-drive-case:
(...) But with four devices, raid10 and the btrfs mode called raid10 will be
the same anyway. (...)
Just to play safe: can I really just add the two disks to the existing btrfs-raid1 and end up with the same level of robustness as (btrfs-)raid10?
Or is the btrfs-wiki outdated and changing raid levels is possible indeed? What would you do in my case?
Thanks
lynix
Offline