Il giorno mar 5 gen 2021 alle ore 07:44 <cedric.dew...@eclipso.eu> ha scritto:
>
> Is there a way to tell btrfs to leave the slow hdd alone, and to prioritize
> the SSD?
You can use mdadm to do this (I'm using this feature since years in
setup where I have to fallback on USB disks for any reason).
>From manpage:
-W, --write-mostly
subsequent devices listed in a --build, --create, or
--add command will be flagged as 'write-mostly'. This is valid for
RAID1 only and means that the 'md' driver will avoid
reading from these devices if at all possible. This can be useful if
mirroring over a slow link.
--write-behind=
Specify that write-behind mode should be enabled
(valid for RAID1 only). If an argument is specified, it will set the
maximum number of outstanding writes allowed. The
default value is 256. A write-intent bitmap is required in order
to
use write-behind mode, and write-behind is only
attempted on drives marked as write-mostly.
So you can do this:
(be carefull, this wipe your data)
mdadm --create --verbose --assume-clean /dev/md0 --level=1
--raid-devices=2 /dev/sda1 --write-mostly /dev/sdb1
Then you use BTRFS on top of /dev/md0, after mkfs.btrfs, of course.
Ciao,
Gelma
