On Mon, 1 Dec 2014, Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote:
> On Sun, Nov 30, 2014 at 3:06 PM, Russell Coker <russell@xxxxxxxxxxxx> wrote:
> > When the 2 disks have different data mdadm has no way of knowing which
> > one is correct and has a 50% chance of overwriting good data. But BTRFS
> > does checksums on all reads and solves the problem of corrupt data - as
> > long as you don't have 2 corrupt sectors in matching blocks.
>
> Yeah. I'm not sure though if openSUSE 13.2 prevents users from
> creating btrfs raid1 volumes entirely, or if it's just an install time
> limitation.
With BTRFS you can make it RAID-1 afterwards. The possibility of data loss
during system install usually isn't something you are concerned about so this
shouldn't be a problem.
> I know that Fedora's installer won't allow the user to create Btrfs on
> LVM, and it probably doesn't allow it on md raid either.
For LVM that's reasonable, for MD-RAID that would be a bug IMHO.
On Mon, 1 Dec 2014, Roman Mamedov <rm@xxxxxxxxxxx> wrote:
> * mdadm RAID has much better read balancing;
> Btrfs reads are satisfied from what's in effect a random drive
> (PID-based balancing of threads to drives), mdadm reads from the
> less-loaded drive. Also mdadm has a way to specify some RAID1 array
> members as to be never used for reads if at all possible ("write-mostly"),
> which helps in RAID1 of HDD and SSD.
True. But that's just a lack of performance tuning in the current code, it
will be fixed at some future time.
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