OSX El Capitan

I have had OSX El Capitan loaded for about 11/2 weeks.
I have my executable files on my internal hard drive and all other files are on 4 external hard drives.
After upgrading I noticed that my one drive, "Photo Edit" wasn't loading to my desktop on boot up. I assumed my external drive needed replacing and ordered one.
Then soon after I noticed that after loading another external drive. "iMac Main" wasn't loaded to the desktop but Photo Edit was loaded. Since then when I boot up one or the other isn't there, never both, but one or the other doesn't show on my desktop.
I have checked thoroughly my connections and all are sound. Also whatever drive loads works normally.
I now have to assume that there must be a problem with the OS and not the drives. My other 2 external drives always open and work fine.
I hope you can help.
Wayne

Wayne, I have five external drives connected just fine, so it isn't a problem in the OS. It's either something in your setup or indoor drives. To help diagnose the problem, we need more information: What Mac, How are the drives connected, are you using a hub, is it powered, what else is connected? What shows up in Disk Utility? Any error messages?

EDIT: Also, what drives and how are they powered?

It would also be nice to know what model and year your mac is. Are you using any sort of hub?

Lisa

lclev said:

It would also be nice to know what model and year your mac is. Are you using any sort of hub?

Lisa

Click to expand...

My About shows the following:
OS X El Capitan v10.11.1(15B42)
iMac (27-inch, Late 2012
Memory 8 GB 1600 MHz DDR3
Startup Disk MacIntosh HD
Graphics NVIDIA GeForce GTX 675MX 1024 MB

It was the second question about a hub so I checked to see that all disks were plugged into the same 10 outlet hub. The two that were not coming on were into a secondary 10 outlet hub that is connected to the primary hub. I changed them to the primary hub and they have all come on successfully through 2 startups.

Thank you for your help. Wayne

MacInWin said:

Wayne, I have five external drives connected just fine, so it isn't a problem in the OS. It's either something in your setup or indoor drives. To help diagnose the problem, we need more information: What Mac, How are the drives connected, are you using a hub, is it powered, what else is connected? What shows up in Disk Utility? Any error messages?

EDIT: Also, what drives and how are they powered?

Click to expand...

I get an error message when I shut down: Your computer was restarted because of a problem. Click Report to see more detailed information and send a report to Apple. I have sent a report to Apple each time it happens and they have not as yet replied or stopped the error message..

This morning I received a post from Lisa.
It was the second question about a hub so I checked to see that all disks were plugged into the same 10 outlet hub. The two that were not coming on were into a secondary 10 outlet hub that is connected to the primary hub. I changed them to the primary hub and they have all come on successfully through 2 startups.

Thank you for your help ... I hope Apple takes care of the error messages.

Excellent. I have had a hub give me fits before so that is why I asked. Glad that was the issue as they are not that expensive of a fix.

Lisa

I have two systems with with Win10 and some of my external drives do not show up,one even just keeps trying making me have to remove battery and then reboot system.
I notice one will work on one system but not on the other,have no idea what the problem is.
With my Mac running El Capitan my small WD USB external drive setup for the Mac OS it loads and works great.

Thank you for your help ... I hope Apple takes care of the error messages.

Click to expand...

They probably won't. Those reports go into a large database of such things and when a sufficient mass of them build up they use that data to prioritize and analyze what to do about the reports. But they probably (almost certainly) won't respond to you on them directly. Your problem was not in the OS, but is in the fact that your drives were starved for power. Do you really need 20 USB connections? And are all of those hubs powered? You may also want to look at the power demands you are placing on those hubs and compare it to what they can handle. If you are driving them near the limits, then when the drives need extra to spin up, move the heads, etc., they may not be getting enough power.

I only use 12 ... two for each external drive - (the drive and a backup) and so far this is the first time I have had any trouble. If it happens again I may have to switch to larger drives. I do a lot of photography and it takes a lot of space.
Another option is to use the cloud which I have been considering.
Thanks again for your help.
Wayne

If by "two for each external drive" you mean the cable has two USB plugs that go into the hub, they are not backups, that's power. The drive needs twice what the standard power is on a USB port, so it takes two and puts them in parallel. So each drive is pulling pretty much full power from two USB ports. And if you put three drives in one hub, thats 6 of the 10 ports drawing max power, which is probably why the drives bog down. If you can get external power supplies for the drives and remove the power demand from the hubs you might have better success. Or get a hub that can take the power demand you are putting on it.

"Two for each external drive" I meant 1 external drive is for my files and another for backup. I have 4 external drives for files and 4 to back up each of those drives.
My hubs each have a USB connection and a power connection so each hub has its own power.
I didn't have any problem before El Capitan and now that I have all my external hard drives in the same hub all seems to be working well.
Sorry for the confusion here. I hope this explains it better.
And Apple has done something to my computer as my error messages have gone away and my system is running very fast. I am now a happy camper.
Thanks for your interest.
Wayne

Ah, ok, I get it now. Glad you got it sorted for now. I only have one drive that depends on USB power, the rest are individually powered. The one that is USB powered travels with me, the rest sit on my desk. I prefer individually powered drives because of the power demands on USB ports. That may change with the new specs on the USB-C ports.