Re: I need to P. are we almost there yet?

[ashford@whisperpc.com]

> Phillip Susi wrote:
>
>> I'm wondering which of the above the BTRFS implementation most
>> closely resembles.
>
> Unfortunately, btrfs just uses the naive raid1+0, so no 2 or 3 disk
> raid10 arrays, and no higher performing offset layout.

> Jose Manuel Perez Bethencourt wrote:
>
> I think you are missing crucial info on the layout on disk that BTRFS
> implements. While a traditional RAID1 has a rigid layout that has
> fixed and easily predictable locations for all data (exactly on two
> specific disks), BTRFS allocs chunks as needed on ANY two disks.
> Please research into this to understand the problem fully, this is the
> key to your question.

There is a HUGE difference here.  In the first case, the data will have a
>50% chance of surviving a 2-drive failure.  In the second case, the data
will have an effectively 0% chance of surviving a 2-drive failure.  I
don't believe I need to mention which of the above is more reliable, or
which I would prefer.

I believe that someone who understands the code in depth (and that may
also be one of the people above) determine exactly how BTRFS implements
RAID-10.

Thank you.

Peter Ashford