Re: Is it possible to have metadata-only device with no data?

["Austin S. Hemmelgarn" <ahferroin7@gmail.com>]

On 2017-02-05 23:26, Duncan wrote:
> Hans van Kranenburg posted on Sun, 05 Feb 2017 22:55:42 +0100 as
> excerpted:
>
>> On 02/05/2017 10:42 PM, Alexander Tomokhov wrote:
>>> Is it possible, having two drives to do raid1 for metadata but keep
>>> data on a single drive only?
>>
>> Nope.
>>
>> Would be a really nice feature though... Putting metadata on SSD and
>> bulk data on HDD...
>
> FWIW, it's on the list to be implemented in the future, but there's a lot
> more things on that list than devs working on btrfs, and the feature
> development and stabilization trend is that features often take much
> longer than anticipated, particularly to properly stabilize (to the level
> of the rest of btrfs, which is in general stabilizing but not yet fully
> stable, so stabilization is relative, here), which has slowed down the
> pipeline of new features due to the devs having their hands full
> stabilizing currently done but not yet properly stabilized features.
There are also a number of higher priority features than this.  While it 
would be a wonderful feature to have, it doesn't exactly have a 
particularly significant impact on broad usability.  Most of the 
features being actively worked on are trying to gain parity (no pun 
intended) with other multi-device storage stacks.  Working quotas, 
parity-RAID, hot-spares, and n-way replication are all pretty 
significant to the usability of BTRFS in a pretty large number of 
situations, which is a large part of why they (other than n-way 
replication) are the primary focus right now for development.