What exactly does the MBLD do for 12+ hours on the first Sunday of every month?

I have three My Book Live Duos.

All of them do the following, and have always done the following (they are all on the latest firmware at the time of this post):

On the first Sunday of every month, starting at about 1:00 AM, the green light blinks showing activity. Access to the drive is extremely slow and limited during this activity. Writing even small amounts of data is pretty much impossible.

The activity finishes somewhere between 12-24 hours later (usually around 2:00 PM).

If I reboot the drive during the activty, the activity does not restart until the first Sunday of the next month. Data seems fine, and drive checks using the web interface return everything normal / no errors.

I would like to know,

WHAT EXACTLY ARE THE DRIVES DOING?

It is extremely annoying, and I would just reboot them to stop it, but since I have no idea what the drives are doing, I don’t know how “bad” rebooting the drives during this activity is.

Someone asked this question here, but got no useful response:

http://community.wd.com/t5/My-Book-Live-Duo/MBLD-6TB-Continously-Blinks-Green/td-p/570460

Hello,

Do you have the latest firmware installed?

Thanks very much for the reply.

Please re-read my post. I stated in the second sentence that all three drives have the latest firmware.

In the other post that I linked, I noticed that that person was also told to check and update the firmware, which did nothing to answer their question.

I feel that this is a simple question with a simple answer.

If you don’t know the answer, I humbly request in the politest way possible, to please find someone who does.

I hate to sound curt or rude, it’s just that I feel like I’m being given a form reply, which, at least to me, is more frustrating than no reply at all.

Thanks again for the help.