External Hard Drive spontaneously ejecting after upgrade to Snow Leopard

System Preferences - Energy Saver has an option to put the disks to sleep. See if toggling that option changes this behavior.

I've been experiencing the same issue ewith external USB drives after updating to 10.6 also.

Firewire connections seem stable still.

For me at first it was happening when waking the machine after sleep but now the drives are disconnecting spontaneously at any time. This means I can't finish any backups which is a little concerning.

I've tried different USB ports and running disk utility checks but that hasn't fixed it.

Tried the earlier suggestion here? (I'd not tend to expect the USB port or Disk Utility verification to alter this behavior. Particularly not when there's a selectable option that seems to point right at the current behavior.)

Thanks, that's a good idea. It was set to not spin the drives down so I turned that option on and restarted just to make sure.

Running a backup now and so far so good. Will post an update when/if I can confirm this has fixed it.

Perhaps the drive hardware was automatically spinning down and because SL hadn't sent a spindown command it assumed that it had been disconnected?

Wow it looks like that was it. Two hours with no random unmounting and have completed a super duper clone and time machine backup from that with no issues.

Thanks!

The root function here is likely the USB hardware capabilities; some USB gear can accept a spin-down and a spin-up, and some cannot. In the latter case, the USB gear needs to be hot-plugged to get it to (re)connect. Try different USB gear, or leave the gear running, or switch to solid-state or more power-efficient gear, or switch to NAS-based gear.

Or leave the host box set to not spin-down the USB gear.

And Leopard client also popped these dialog boxes, too. This dialog sequence was very common with a ExpressCard SD card reader I dealt with.

appletonian wrote:

Although it might technically solve the problem to never put hard drives to sleep, it's not particularly energy efficient for me as I have a number of external drives connected to my machine at any given time.

You misunderstood my post - after updating to 10.6 the drives were set to NOT spin down, after changing them TO spin down they never disconnected.

I wonder if the Snow Leopard bug might be that the drives hardware does spin down but the OS is not expecting it because of the energy saver setting so assumes it has been disconnected.

Other threads I've been following have also reported that this has been fixed in 10.6.1 so it might be worth updating if you have not already done so.

I am also facing the problem. The same thing under bootcamp windows 7 it is okey. Only with snow leopard it keeps on ejecting. My external hard disk have their own power souce. When i type something on spotligh search, it ejects the disk some times. With the update 10.6.1 it is not solved. The same thing is happening again.

This looks to be an entirely different question. If you're typing information and your drives get ejected, then that's likely not the power savings mechanism that's being discussed in this thread. Please start your own thread for the question.

Here's the [Snow Leopard Mac OS X client discussion forum|http://discussions.apple.com/category.jspa?categoryID=263]; I'm guessing that you're probably not running the Server version of Mac OS X here.

When you start your new thread, please also identify the details of what you're working with for a Mac (if it's the same MacBook Pro you've been troubleshooting with the ACPI errors a while back, or otherwise) and what is in use out on the USB. USB hubs whether powered or not, USB devices, etc. And some of what you're describing might be consistent with some part of the USB might be drawing too much power from the USB, or with a faulty USB device, or with too much hanging off the USB.

rbmanian75 wrote:
... When i type something on spotligh search, it ejects the disk some times.

I thought that was interesting so I went to Spotlight and discovered it in the midst of indexing TM! I didn't try a search, I waited until it was done - that was interesting as well, because the "time remaining" values were incrementing, not descending! Then I realized that TM was preparing for a backup - once that backup was complete, Spotlight quickly finished indexing TM.
So I'm guessing you might be trying to use Spotlight while it's busy indexing TM and that' has something to do with the disk ejecting.

After a phone call to Apple Canada yesterday I've narrowed my problem down to something happening between TM and the computer shutting down hard disks. When the computer goes to sleep the screen sleeps but the computer doesn't (I've got both set to sleep after 3 min so I can watch what's going on). The light on the lower right comes on, but doesn't go to blinking - the TM is making noises - indexing the TM disk I'm guessing - it's not doing a backup, I don't think. TM is active for more than 10 minutes. I have no idea how long it takes for the light to go to blinking (the computer to actually go to sleep - a long time - I've sat and waited, and waited (at least 15 minutes). I've finally left the room and returned after about 20 minutes and the light's now blinking. It takes a mouse click to wake the computer (I remember a movement of the mouse was all it took before I did this upgrade to SL). The screen wakes immediately, TM is still mounted on the desktop - then the Macintosh HD wakes and TM ejects and I get the error message "Disk improperly ejected..."! The TM disk remounts itself immediately and the first thing TM does is reindex the drive (at this point the info on first and latest backup is empty, until the indexing is complete). The thing is, it doesn't do it every time the computer finally goes to sleep (the light goes to blinking)!

That's as far as I've got so far. Can anybody add to this? I've been working on this nearly hourly since about 10:00 pm last evening. I'd like more information before I call Apple back.

jimmykl wrote:
Other threads I've been following have also reported that this has been fixed in 10.6.1 so it might be worth updating if you have not already done so.

I've done the update to 10.6.1 - still having the problem

MrHoffman wrote:
Or leave the host box set to not spin-down the USB gear.

The ejecting happens whether I've checked "Put hard disks to sleep whenever possible" or not (Energy Saver Control Panel) At the moment I've got it unchecked

+1 for the same issue here...