> The workaround is simple, though: polling /proc/mdstat works fine for
> both disk failure and disk resync event.
That's exactly what mdadm --monitor does, BTW.
After the detection of an
> event I can read /sys entries, it's much more comfortable than parsing
> human-readable /proc/mdstat.
Yes, and internal MDADM IOCTLs are even better (but you need to code C).
Alex.
>
> Mikhail Balabin
>
> 2012/1/8 Alexander Lyakas <alex.bolshoy@xxxxxxxxx>:
>> Hi,
>> well, at least according to 2.6.38-8 kernel code, this attribute is
>> notified in 3 cases:
>> # When the array is started (e.g., via RUN_ARRAY ioctl)
>> # When "reshape" is initiated via sysfs
>> # When a spare is activated after successful completion of
>> resync/recover/check/replair
>>
>> If you want to monitor changes in the array, what works for me is the following:
>> # Arrange some script/executable to be called by MD monitor
>> # Every time your script/executable is called, go and check the
>> details you are interested in (e.g., mdadm --detail). The MD monitor
>> also provides the description of the event (see man mdadm for possible
>> events), but at least for me it is not always accurate, especially
>> when there are several very fast changes in the array.
>> # If you want to monitor resync/recover/check/repair progress, you
>> need to specify both --delay and --increment options to MD monitor.
>>
>> Alex.
>>
>>
>> On Thu, Jan 5, 2012 at 10:34 AM, Mikhail Balabin <mbalabin@xxxxxxxxx> wrote:
>>> Hi!
>>>
>>> I'm playing around with monitoring software raid status via sysfs
>>> entries. In my case it's a raid1 array. According to
>>> Documentation/md.txt any md device with redundancy should contain file
>>> "degraded" (for example, /sys/block/md0/md/degraded) with the number
>>> of devices by which the arrays is degraded. It is stated that this
>>> file can be polled to monitor changes in the array, but it does not
>>> work for me. Here is my (stripped-down) python code:
>>>
>>> import select
>>> fileName = "/sys/block/md0/md/degraded"
>>> epoll = select.epoll()
>>> while(True):
>>> file = open(fileName)
>>> status = file.read()
>>> print(status)
>>>
>>> epoll.register(file.fileno(), select.EPOLLPRI|select.EPOLLERR)
>>> epoll.poll()
>>> print("==== poll ====")
>>> epoll.unregister(file.fileno())
>>> file.close()
>>>
>>> The script works fine for /proc/mdstat or /proc/mounts, but does not
>>> show any events for /sys/block/md0/md/degraded. Is there a problem in
>>> my code? Or is the documentation inaccurate?
>>>
>>> Mikhail Balabin
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