Re: Small fs

[Chris Murphy <lists@colorremedies.com>]

On Sun, Sep 11, 2016 at 10:54 PM, Duncan <1i5t5.duncan@cox.net> wrote:

> On the bright side, the double-whammy of being under such tight
> filesystem size constraints, coupled with finding out you have less than
> half the space of the filesystem actually available due to default-mixed-
> mode AND default dup-metadata (thus dup everything),

I'm not following what you mean by default dup everything. You mean
that's how it used to work? Because on a real USB stick, 2GiB:


[chris@f24m ~]$ mkfs.btrfs -M /dev/sdb
btrfs-progs v4.7.2
See http://btrfs.wiki.kernel.org for more information.

probe of /dev/sdb failed, cannot detect existing filesystem.
ERROR: use the -f option to force overwrite of /dev/sdb
[chris@f24m ~]$ sudo mkfs.btrfs -M /dev/sdb
btrfs-progs v4.7.2
See http://btrfs.wiki.kernel.org for more information.

Label:              (null)
UUID:               237d8ab9-b22f-435c-bbd8-2117afa1760c
Node size:          4096
Sector size:        4096
Filesystem size:    1.87GiB
Block group profiles:
  Data+Metadata:    single            8.00MiB
  System:           single            4.00MiB
SSD detected:       no
Incompat features:  mixed-bg, extref, skinny-metadata
Number of devices:  1
Devices:
   ID        SIZE  PATH
    1     1.87GiB  /dev/sdb



Whereas without the -M


[chris@f24m ~]$ sudo mkfs.btrfs -f /dev/sdb
[sudo] password for chris:
btrfs-progs v4.7.2
See http://btrfs.wiki.kernel.org for more information.

Label:              (null)
UUID:               a7c79550-10b8-4a4c-9b23-9c9110e30121
Node size:          16384
Sector size:        4096
Filesystem size:    1.87GiB
Block group profiles:
  Data:             single            8.00MiB
  Metadata:         DUP              95.56MiB
  System:           DUP               8.00MiB
SSD detected:       no
Incompat features:  extref, skinny-metadata
Number of devices:  1
Devices:
   ID        SIZE  PATH
    1     1.87GiB  /dev/sdb



So with -M, it's single by default..


-- 
Chris Murphy