On 6/27/20 11:09 PM, Chris Murphy wrote:
On Sat, Jun 27, 2020 at 9:25 PM Gabriel Ramirez <gabrielo@xxxxxxxxxx> wrote:
On 6/27/20 9:06 PM, Chris Murphy wrote:
Just a PSA: btrfs raid1 does not have a concept of automatic degraded
mount in the face of a device failure. By default systemd will not
even attempt to mount it if devices are missing. And it's not advised
to use 'degraded' mount option in fstab. If you do need to mount
degraded and later the missing device is found (?) you need to scrub
to catch up the formerly missing device to the current state.
That seems a step back,
Yes. You do gain self-healing and unambiguous scrubs, which apply only
to the used portion of the drives. Three steps forward half step back?
The priority would be to replace the failing/failed drive before a
reboot. Yes, the use case where the drive dies on startup and
unattended boot is needed is weaker.
yeah, but coming from mdadm, I (will be)/(was) expecting the same or
better from a new filesystem, or documentation to resolve the situation
"shutdown, replace the disk, boot with another media etc..."
because when the problem happens, googling sometimes fails too
'btrfs replace' -
There will be a "decoder ring" guide to adapt to various commands. A
super rough draft, more of a quick and dirty concept, is here:
https://fedoraproject.org/wiki/User:Chrismurphy/lvm2btrfs
And hopefully this will expand into "how do I?" step by step use cases.
that will be appreciated because btrfs seems to have many options
Of course the single drive case folks aren't expected to know btrfs
commands. If they want more detailed info however, they're there.
start the machine with all services running
create the disk partitions, if needed reboot again, and add the
partitions to the raid devices
Off hand I'm not thinking a reboot is needed. You can partition the
replacement drive, and then do 'btrfs replace' - whether it's
pre-emptive or for a missing device. This command combines: mkfs /
device add, and replication of raid1 block groups using a variation on
scrub.
at least one shutdown, start is needed (I have to open the computer
case, replace the hard disk)
another reboot if after partition the drive the kernel complains about
"the current partition will be used until reboot"
Gabriel
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