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Date:      Wed, 19 Aug 2020 22:06:04 +0530
From:      Manish Jain <bourne.identity@hotmail.com>
To:        freebsd@dreamchaser.org, Polytropon <freebsd@edvax.de>, Christoph Kukulies <kuku@kukulies.org>
Cc:        Ruben via freebsd-questions <freebsd-questions@freebsd.org>
Subject:   Re: Correct way to disconnect/eject an USB hard disk ?
Message-ID:  <DB8PR06MB64420C592F160459B28CFD02F65D0@DB8PR06MB6442.eurprd06.prod.outlook.com>
In-Reply-To: <b9b46ecb-b1ef-8f67-7b41-ae3cf0d3864b@dreamchaser.org>
References:  <C6B11926-65BE-4A05-B421-9F3E9C9AACF6@kukulies.org> <20200819142952.3686baa8.freebsd@edvax.de> <DB8PR06MB64427319E175193D1B828135F65D0@DB8PR06MB6442.eurprd06.prod.outlook.com> <b9b46ecb-b1ef-8f67-7b41-ae3cf0d3864b@dreamchaser.org>

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On 2020-08-19 21:12, Gary Aitken wrote:
> Can you explain why I have seen umount commands return, and then the
> USB device "activity" light keeps blinking?  I have on occasion waited
> for a while and it keeps blinking, and eventually I just unplugged it.

No idea, Gary.

But umount only returns when pending I/O has been flushed to the device. 
If the device's activity LED still keeps blinking, there are two 
explanations I can think of :

1) The LED sensor is either faulty or is simply signalling availability 
of power (in case there is no separate power LED).

2) The device has some internal flash storage intermediate to its main 
storage area. While umount could return when data has been sent into the 
flash buffer, the device still has to internally reallocate the data to 
main storage (as might be the case with SSHD: solid state hybrid disk). 
In such case, it would be prudent to wait for the LED to stop blinking 
before unplugging the device. But if the LED keeps blinking forever, I 
would think there is some fault with the LED itself.

Poly, your comments ?


Regards,
Manish Jain



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