Mac Pro: Mysterious "smoke detector" squeal??

[kirkbross]

So last night during the shutdown sequence (i.e., after I initiated shutdown and before the computer powered down) my early 2008 Mac Pro (running Lion on a Vertex 2 SSD) made a prolonged squeal that sounded literally like a smoke detector going off. It was long, high pitched and VERY LOUD. In the 15 years I've been using Macs I've never heard this sound.

I had two external SATA enclosures running which I had powered off around the same time so it's possible it could have been one of those. It didn't sound like a fan motor tweaking out, it was like an "intentional" sound if that makes sense.

The windup... everything seems normal. After a few seconds, the shutdown completed and when I rebooted everything was fine and it hasn't happened since.

Any clues?

 

[codymac]

Is it on a UPS?

 

[kirkbross]

Is it on a UPS?

Nope... just plugged into a passive power strip.

I managed to reproduce the sound repeatedly and pinpointed it to the eSATA drives.

When I eject and then power off either or both of my two eSATA drives, the squeal happens and stays squealing until I turn the drive back on.

When I turn the drive back on, the squeal stops (and surprisingly the eSATA drive remounts).

I have the eSATA drives connected to a NewerTechnologies MAXPower eSATA 6GB PCIe 2.0 Controller Card.

The solution for now seems to be to power down the Mac Pro before shutting off the eSATA drives. Weird.

 

[codymac]

Nope... just plugged into a passive power strip.

So much for my first thought: that something had inadvertently caused a UPS to kick in and alarm.

That does sound odd.

 

[ActionableMango]

Possibly a glitch on the internal speaker used for the startup chime.

 

[DasShrubber]

A loud squeal as in a capacitor about the fail?

 

[kirkbross]

OP: I managed to reproduce the sound repeatedly and pinpointed it to the eSATA drives (as the cause). The actual "generator" of the sound is still unknown.

Here's when it happens: when I eject/trash and power off either of my two eSATA drives, the squeal happens and stays squealing until I turn the drive back on.

When I turn the drive back on, the squealing tone stops and surprisingly the eSATA drive remounts. (I always thought eSATA drives were not hot swapable).

Note: I have the eSATA drives connected to a NewerTechnologies MAXPower eSATA 6GB PCIe 2.0 Controller Card. This might be the source of the actual sound.

All I have to do is power down the Mac Pro before shutting off the eSATA drives, and there are no other symptoms, but it's still a bizarre sound.

 

[DasShrubber]

DId it sound like any of these?

http://datacent.com/hard_drive_sounds.php

or if your want open up the eSata drive and spot the failing fan.

 

[flatfoot]

To the OP: Install the WebGUI for your HighPoint eSATA card (I guess you're using one) and turn off the alarm of the card.