[mythtv-users] Manage recording storage group with btrfs subvolume

[James Linder]

> On 10 Jan 2021, at 11:25 pm, David Hampton <mythtv at love2code.net> wrote:
> 
> On Sun, 2021-01-10 at 19:21 +0800, James Linder wrote:
>> 
>> 
>>> On 10 Jan 2021, at 6:06 pm, Mike Perkins <
>>> mikep at randomtraveller.org.uk> wrote:
>>> 
>>> On 10/01/2021 02:27, Richard Shaw wrote:
>>>> I'm looking at moving to a 4 drive raid1 array (and perhaps
>>>> converting to
>>>> raid5 later) btrfs array. Most of the space will be used for
>>>> media but I
>>>> want to keep 1TB for recordings.
>>>> The problem is that btrfs will share free space among subvolumes
>>>> by default
>>>> and I don't know if there is  a quota method that will limit free
>>>> space
>>>> reporting so that the backend will expire recordings properly
>>>> like on a
>>>> dedicated filesystem.
>>>> Anyone else run into this and have a solution?
>>> I run my "raid" volumes under LVM. That way I can allocate discrete
>>> volumes[1] to each function and the free space is not shared
>>> between them.
>>> 
>>> [1] Each volume can them be formatted a different way as required.
>> 
>> Richard why would you not partiton your disks *exactly* as you want,
>> rather than what your vendor (suse ??) decided what was good for most
>> people. When I looked I decided that btrfs was not what I wanted on
>> my myth server
> 
> For an opposite viewpoint, I've been running a four drive btrfs raid-6
> setup for about a decade as my recordings storage volume, and have been
> very happy with it. I only have the one subvolume though, so I've never
> looked at the quota support.

David my biggest concern was the risk of disk damage in the event of sudden power fail. EXT4 has proved robust and has caused me no issues on 

Filesystem      Size  Used Avail Use% Mounted on
/dev/nvme0n1p2   20G  8.7G   10G  47% /
/dev/nvme0n1p5  1.7T  1.1T  539G  66% /store
/dev/nvme0n1p3   98G   44G   50G  47% /home
/dev/sda1       3.6T  1.7T  1.8T  49% /store/Movies
/dev/nvme0n1p1  250M   12M  238M   5% /boot/efi
/dev/sdb1       4.6T   59G  4.3T   2% /backup

James