Yes, it HAS to be El Capitan. I've tried every fix: checked/repaired the drive; zapped PRAM and all the others; tried both USB ports. Eventually, I'll get the error message. I've looked in the Console. It looks like El Cap "loses" the information it needs to make a connection to the drive. Yup. It's a mess. A.
USB3 via a PCi board in MacPro can be dodgy when the computer sleeps. My experience is the power to the board is cut when the computer sleeps and while the board will power back up when the machine wakes, it does not always wake up the drive, which then "disappears". Here is the solution I found: I connected the drive to a powered USB3 hub that is connected to the USB3 board in the computer. The hub power apparently is enough to allow the computer to sleep and allow the drive to wake when the computer wakes. The native USB 2.0 ports appear to handle sleep differently.
I just started having this problem yesterday. I'm on El Capitan 10.11.1 on my late 2013 iMac. I have four externals -- two WD, 1 Lacie, 1 Iomega. Two are plugged directly into the computer, two plugged into an unpowered USB3 hub. All are now being "improperly ejected" when the computer sleeps.... This exact drive setup has been in place on this computer for months, probably years. Similar setups have functioned properly for many years. Now, though, not so much, and, yeah, I'm annoyed.
It is not El Capitan specific. This happens in Yosemite also. Most cases involves Seagate Go Flex drives. USB connection.
I've found that this happens, for me anyway, when I use a cable longer than the original length cable that comes with the drive (12-16 inches). When I get the disc ejecting problem it seems to coincide with the use of a longer (3 feet) cable. Can anyone corroborate this with their issue of 'external disc ejecting'?
Having the same problem here with my 3 TB porsche design Lacie drive. Having errors every time my MBPR (late2013) goes to sleep. Didn't have this before EL freaking Capitan. The disk is connected through a usb 3.0. Just reseted the SMC and PRAM to see how it goes but as I can tell from the posts, i'll have no success. Come on Apple, fix this!
I installed some software for my phone and had to reboot my Mac, now I no longer have the problem with my external USB 3.1 drive and Time Machine. Hope I don't have to ever reboot it again!
My "My Passport Slim" worked perfectly on Yosemite. As soon as the upgrade to El Capitan I started getting the messages. I seriously doubt it's a hardware issue with the drive. So frustrating. I'm on 10.11.3, and waited this long to upgrade because I wanted to avoid issues like this. I guess next time I'll wait until .4 or .5.
To help prevent this ongoing problem. I turn of Put Hard Disk to sleep. Now the iMac won't go to sleep at all. Even when nothing is accessing iTunes Home Sharing. The disk won't eject, but the iMac will run 24/7. Maybe Apple should stop going goofy with Dr Dre and Social Life trends and FOCUS on having some real reliable quality software and hardware. What a stupid mess this is.
I have had this problem for about 3 months. My disk is a Seagate Backup Plus Slim 2TB usb3.0. However I don't get this problem with my WD-elements using same cable, so it might be my disk... Also If working with documents on that disk (photoshop) and computer goes to sleep, PS crash on wake up and my work is lost. It's obvious that the disk can't be reached and thus PS loses the connection to the file. So far I have backed up the disk. One way to solve it is to turn of energy save in OS. It only happens when computer goes to sleep.
I think it's El Capitan, at least in my case. I have a Mac mini Model Name: Mac mini Model Identifier: Macmini6,2 Processor Name: Intel Core i7 Processor Speed: 2.3 GHz Number of Processors: 1 Total Number of Cores: 4 L2 Cache (per Core): 256 KB L3 Cache: 6 MB Memory: 16 GB Running System Version: OS X 10.11.4 (15E65) Kernel Version: Darwin 15.4.0 My external drive is Device Name: External HDD Media Name: Fantom External HDD Media I have two of the drives mentioned above. Bought at the same time from the same place, both connected via usb, both in place since I purchased the mini. They sit side by side where they have sat for the entire time I've owned them and the computer. Nothing has changed positions, no new cabling, no electrical changes and so on. External Drive 1 has files on it (1/2 TB give or take) External Drive 2 is my Time Machine Volume (yes I realize it is the same size as my external drive and could not hold my external drive files plus the mac mini files if both were at capacity) The drive that gets disconnected from El Capitan is always Drive 1, the drive not functioning in Time Machine capacity. This has only happened since upgrading to the latest version of El Capitan. I was on El Capitan for awhile without issue, but the latest upgrade brought the issue. Presumably the time machine volume has a trickle of OS activity that keeps it online and that accounts for only one of them going missing. At first I thought my drive might be failing, but if I power it off and back on, it always shows up in the finder. I ran first aid with disk utility, everything is fine. My conclusion is that it's the OS. Hoping an update takes it away as silently as it appeared.
I forgot about the dropped drive issue but saw some people were still having problems. I have two WD MyBook, two Seagate and an old Seagate Barracuda in a generic housing, all on the USB 3 bus of a 2013 Mini i7 (OS 10.11.4). I was able to solve the dropped drive issue by switching out my USB hubs. Of course, direct connection to the Mini is best but with only 4 ports I need a hub. I went through four hubs before I found one that didn't drop my HD drives and flash drives: Dyconn. 10.11x is picky about hubs as basically any hub worked with OS 10.8.5.
You can try this in a Terminal window: Code: sudo pmset -a autopoweroff 0 This solved my USB 3.0 problems.
I jus started to experience this issue with my Late 2015 iMac and USB 3.0 connection for external nuTech HDD. I didn't notice this a few weeks ago. Any known solution?
What's the model identifier? Make and model please. If it's rotational media, the problem may involve the disk not spinning enough in good time.