This. So much this.

After being burned badly by the documentation / wiki etc making RAID5/6
seem stable, I think its a joke how the features of BTRFS are promoted.

A lot that is marked as 'Implemented' or 'Complete' is little more than
a "In theory, it works" - but will eat your data.

Having a simple reference as to the status of what is going on, and what
will eat your data would probably save Tb's of data in the next few
months and lots of reputation for BTRFS...

On 11/09/16 18:55, Waxhead wrote:

I have been following BTRFS for years and have recently been starting to
use BTRFS more and more and as always BTRFS' stability is a hot topic.
Some says that BTRFS is a dead end research project while others claim
the opposite.

Taking a quick glance at the wiki does not say much about what is safe
to use or not and it also points to some who are using BTRFS in production.
While BTRFS can apparently work well in production it does have some
caveats, and finding out what features is safe or not can be problematic
and I especially think that new users of BTRFS can easily be bitten if
they do not do a lot of research on it first.

The Debian wiki for BTRFS (which is recent by the way) contains a bunch
of warnings and recommendations and is for me a bit better than the
official BTRFS wiki when it comes to how to decide what features to use.

The Nouveau graphics driver have a nice feature matrix on it's webpage
and I think that BTRFS perhaps should consider doing something like that
on it's official wiki as well

For example something along the lines of .... (the statuses are taken
our of thin air just for demonstration purposes)

Kernel version 4.7
+----------------------------+--------+-----+-------+-------+--------+-------+--------+

| Feature / Redundancy level | Single | Dup | Raid0 | Raid1 | Raid10 |
Raid5 | Raid 6 |
+----------------------------+--------+-----+-------+-------+--------+-------+--------+

| Subvolumes                 | Ok     | Ok  | Ok    | Ok    | Ok   | Bad
  | Bad    |
+----------------------------+--------+-----+-------+-------+--------+-------+--------+

| Snapshots                  | Ok     | Ok  | Ok    | Ok    | Ok     |
Bad   | Bad    |
+----------------------------+--------+-----+-------+-------+--------+-------+--------+

| LZO Compression            | Bad(1) | Bad | Bad   | Bad(2)| Bad    |
Bad   | Bad    |
+----------------------------+--------+-----+-------+-------+--------+-------+--------+

| ZLIB Compression           | Ok     | Ok  | Ok    | Ok    | Ok     |
Bad   | Bad    |
+----------------------------+--------+-----+-------+-------+--------+-------+--------+

| Autodefrag                 | Ok     | Bad | Bad(3)| Ok    | Ok     |
Bad   | Bad    |
+----------------------------+--------+-----+-------+-------+--------+-------+--------+


(1) Some explanation here...
(2) Some explanation there....
(3) And some explanation elsewhere...

...etc...etc...

I therefore would like to propose that some sort of feature / stability
matrix for the latest kernel is added to the wiki preferably somewhere
where it is easy to find. It would be nice to archive old matrix'es as
well in case someone runs on a bit older kernel (we who use Debian tend
to like older kernels). In my opinion it would make things bit easier
and perhaps a bit less scary too. Remember if you get bitten badly once
you tend to stay away from from it all just in case, if you on the other
hand know what bites you can safely pet the fluffy end instead :)

-- 
Steven Haigh

Email: netwiz@crc.id.au
Web: https://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897