Re: Monitoring for disk failures

[Duncan <1i5t5.duncan@cox.net>]

Alin Dobre posted on Mon, 27 Jan 2014 11:43:33 +0000 as excerpted:

> I am trying to create a very simple script that would alert in case of
> disk failures from a RAID Btrfs.
> 
> Digging into the code, I have noticed that the "btrfs fi sh" command
> should display a warning if there is a missing disk. However, testing in
> a Qemu, I used "drive_del" via QMP to remove a "live" SCSI drive,
> already mounted as part of a RAID10 array, the "fi sh" command still
> gave no indication that the drive is missing. Then, I tried removing a
> scsi disk from the host via "echo 1 >/sys/block/sdX/device/delete" to
> actually make the kernel SCSI host forget about it, and "fi sh" still
> doesn't show anything.
> 
> I have tested using btrfs-progs v3.12 and kernel 3.13.0.

Without actually trying it here... I believe by default that'd update 
only when there was an I/O error.

Did you try btrfs filesystem show --all-devices?  That scans differently.

If that doesn't work try btrfs device scan first as that updates the in-
kernel list, then filesystem show.  Alternatively, monitor the kernel log 
for output as the scanned devices show up there.

And if /that/ doesn't work, try show, followed by a probe of all the 
devices listed by show.  But I strongly suspect a device scan will force 
the update you're looking for.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman