Another user-space tool to look at is xosview. The current release 
version uses /proc/mdstat (and is terminally broken as a result), but 
it's being updated to use /sys/block/...

Cheers,
Wol

On 14/02/17 14:43, Tim Small wrote:

Hello,

A design question for a user-space RAID monitoring tool.  The tool is
intended to export machine-readable md state so that the system owners
can creating automated alert policies etc.

Should it get its information on md device state from /proc/mdstat, or
/sys/block/*/md/ as a data source, or should it use the ioctl interface
that mdadm uses (on the basis that this is more complete / heavily tested).

I assume the issues are:

. usability (/proc/mdstat is intended to be human-readable so machine
parsing it seems bleugh - it's also incomplete?)

. stability (perhaps /sys/block/*/md/ is less stable than the ioctl or
proc interface?  Or perhaps it's just fine and won't break in
backward-incompatible ways?).

Any thoughts?

Should I see which way the recent "add bad block flag to disk state"
patch-set thread goes?

Tim.
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