Do HDD have brown-out detection ?

[expert_vision]

I bought a SATA-USB adaper which I use with a 2.5' HDD (WD800BEVS) as an external HDD and when I disconnect it there is a squeak noise.

I do know that the heads are kept apart by a thin layer of air caused by the air drag due to the spinning plates. Now if the plates stop spinning, the heads fall on the plates and ...

Do HDDs generally have brown-out detection, slamming the heads off the plates before they stop spinning ?
Is there way to gracefully stop the HDD (besides the useless "Safely Remove Hardware" Windows feature) ?

In 3+ years of operation inside a laptop, it got around 100 "Power-Off Retract Count" events in the S.M.A.R.T table. Now this value is incremented every time I disconnect the USB adapter, which clearly indicates the HDD is not shutting down gracefully.
I wonder how the commercial external HDDs work, since they use normal HDDs.

Basically, every time I disconnect the HDD I clench, due to the noises it makes.

 

[blazorthon]

HDD disks don't stop spinning immediately (even if power loss is immediate) because they have a decent amount of momentum (they are spinning at least around 5400rpm after all). Hard drives typically don't have issues with immediate power loss beyond the cache might have data that wasn't flushed, depending on settings. For example, laptops usually don't even worry about that because they are usually set up to only cache reads and not writes.

Brown outs are usually not very dangerous to computers because the power supply is fairly robust about power swings, especially down. Extended periods of time with low voltage input will cause problems, but short voltage drops from brown outs are not particularly dangerous and do not have a significant effect on the output voltages. Ripple will be worse and the power supply will lose efficiency (causing heat generation to go up), but again, short periods of time are not very dangerous. Data loss on a hard drive under these situations is almost impossible.

Now if the noise is in fact caused by a head touching where it should not before the disks come to a stop, then that might mean the hard drive has a mechanical defect- that should not happen even in blackout conditions because hard drives are manufactured for air to be able to pass from the hard drive to outside of it or the other way around to keep the pressure inside the drive consistent. Such a defect where this is not properly happening can cause data loss by damaging the hard drive, but that's only speculation as to what is causing the noise.

Out of curiosity, why was the laptop experiencing brownout or blackout conditions very often?

 

[RealBeast]

Drives should not make such noises when disconnected.

On the topic of USB connected drives -- they are far less robust than SATA connected drives in terms of data loss issues. If a USB connected drive is doing a write when powered off there is a good chance that you will lose all the data on the drive (you can scan the storage forum and see the many data loss issues). Always best to eject the drive before disconnecting or powering down, and do not rely on USB drives as your sole backup for important data.

You may also want to look into getting a UPS that has the ability to shut down your machine if you have frequent power loss. APC software is quite useful for that and their UPSs are very good quality.

 

[expert_vision]

Out of curiosity, why was the laptop experiencing brownout or blackout conditions very often?

The laptop has no power issues. Let me clarify. I upgraded my internal laptop HDD from an old 80 GB one to a newer one, and the old one works perfectly fine, the S.M.A.R.T. values are actually quite good, so it's healthy.

The problem is that I now use the old one with a USB-SATA adapter and is not really hot swap-able, because cutting of power to an HDD while it's spinning is not really a good idea, busy or not, doesn't matter. In fact, every time I unplug it, the "Power-Off Retract Count" event is incremented in the S.M.A.R.T. table, so the HDD is not shutting down gracefully.
From wikipedia:

Also known as "Power-off Retract Count" per conventional HDD terminology. Raw value reports the number of unclean shutdowns, cumulative over the life of an SSD, where an "unclean shutdown" is the removal of power without STANDBY IMMEDIATE as the last command (regardless of PLI activity using capacitor power).

My only fear is that the heads fall on the plates during power blackouts, but common sense tells me that they have included a brown out detection, so it detects when it's about to lose power, and it throws the heads off the plates making a click sound when it hits the end. But what worries me is the typical whine until the plates stop spinning. By the way, they stop pretty fast .. < 2 seconds.

Always best to eject the drive before disconnecting or powering down

Well, that is not enough. Doing that will only stop accessing the disk, but it's still spinning, doing a normal clicky thing every now and then. And cutting off power at that time will trigger an "Power-off Retract Count" S.M.A.R.T. event.

In fact, I discovered that if I wait 10 minutes while the disk is idle, it will go in to sleeping mode, when he either slows down a lot or completely stops spinning (I can't tell, it's too quiet), and now it's safe to disconnect whitout incrementing "Power-off Retract Count" event, and no weird noises. If I do eject the drive, it will never go in to sleeping mode.

I wonder if there is an application to send STANDBY IMMEDIATE command as mentioned in the wikipedia quote above.

 

[RealBeast]

I don't use Windows safe eject, I use a free app called HotSwap! from HERE that is far more reliable and also will spin the drive down.