Time Machine - External HD Loses Recognition?

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First talking about my wife's iMac (early 2013) which has been taken from 10.8.x and is now on 10.10.1 - I've used Time Machine (TM) from the start w/ a 1 TB Seagate external HD (Mac OS formatted) - I just check this computer every other day but the HD when recognized is on the desktop as an icon, but just intermittently disappears for no reason - why?

The HD is plugged directly into a USB slot on the back of the iMac & TM seems to be working fine, i.e. when connected and working! This has been occurring through 3 versions of OS X, so what is the issue? Options seem to be TM, my computer, and/or the Seagate HD - I'm sure others have had the same issue. Now, not a big problem if I go in and look - simply disconnect & reattach and the drive icon reappears - curious & thanks. Dave :)
 
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MacInWin

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I had similar problems with Seagate drives. Seagate apparently has some drives with "power saving" that shuts them down if they are idle for a certain period of time. When they go to that mode, OS X sees them as gone and unmounts them. If you can disable that mode somehow, it may fix it, but if not, you'll have to live with it. WD drives don't seem to have that function, which is why I prefer them.
 
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If your drive is like my Seagate, the power is dependent on the USB slot. After fiddling with power settings, I finally connected the drive to a USB hub which has power directly from a UPS.
 
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Thanks Guys for the comments - it's the Seagate Backup Plus Slim 1 TB USB 3.0 - plugged directly into the back of the iMac, so powered. As I recall, I did do a firmware update last year, but would need to check. Seagate also has an OS app called Dashboard that likely could give me more information and even allow adjustments of the sleep times if that is the issue - not sure if it has been updated and compatible w/ Yosemite which I just installed (and seems to be working well @ the moment).

But the HD behaves unpredictably, i.e. seems to stay attached for days on end and then disconnects more often - I do TM on my laptop about once a week, so will simply make it a habit to check the iMac more often. Dave :)
 
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i hate seagate honestly the drives fail they only provide fixes and firmware updates trying to correct faulty drives and the firmware updates can usually be installed only in windows they are really not a good drive to have get a wd my book of a wd my cloud
 
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Yeah, Dave, I found USB to be flaky that way, which is why I went to Firewire. USB seems to just drop connections sometimes. Might be a cable gets jiggled, or cosmic rays, or something, but TM to a USB drive never worked reliably for me. But if you only do TM once a week, just make sure the drive is there just before you trigger the backup.
 
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Yeah, Dave, I found USB to be flaky that way, which is why I went to Firewire. USB seems to just drop connections sometimes. Might be a cable gets jiggled, or cosmic rays, or something, but TM to a USB drive never worked reliably for me. But if you only do TM once a week, just make sure the drive is there just before you trigger the backup.

Hi Jake and others - well, that's another idea, i.e. use a non-USB option; my iMac just has 'Thunderbolt' (TB) ports (x2) and I was looking on Amazon & on OWC, and found the latter (pic below) for $159 (including the cable), nearly twice as much as my current USB Seagate HDs.

So, just curious about that option in maintaining a reliable connection? Would appreciate any comments from those who may be using TB external HDs for TM and/or other backups?

And a related question - if I were to purchase such a drive, can I transfer my current TM iMac backups to it or would it be better to just start over but keep the old Seagate HD just in case I would need data from the past (just goes back 18 months). Dave :)
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MacInWin

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Yeah, TB hardware is expensive. I don't have a TB drive, but my. TB monitor works reliably, and the FireWire drives attached to it are reliable, so a direct TB drive should be good
 
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Hi Jake and others - well, that's another idea, i.e. use a non-USB option; my iMac just has 'Thunderbolt' (TB) ports (x2) and I was looking on Amazon & on OWC, and found the latter (pic below) for $159 (including the cable), nearly twice as much as my current USB Seagate HDs.

So, just curious about that option in maintaining a reliable connection? Would appreciate any comments from those who may be using TB external HDs for TM and/or other backups?

And a related question - if I were to purchase such a drive, can I transfer my current TM iMac backups to it or would it be better to just start over but keep the old Seagate HD just in case I would need data from the past (just goes back 18 months). Dave :)
.

Hello ALL - well I decided to purchased the OWC TB external drive for my TM backup on our iMac - been running a Seagate external HD for nearly 18 months - please see my previous post above in bold - would appreciate some advice to switch over from the older HD to the newer one which should arrive early next week - thanks for comments. Dave :)
 

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I would keep the Seagate for as long as you feel you need to. I have done the exact same thing when switching to a new external hard drive for Time Machine. Once I'm sure that I will not have to use the older drive to restore from, I then format it to use for something else or throw it away if it's outmoded.
 
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I would keep the Seagate for as long as you feel you need to. I have done the exact same thing when switching to a new external hard drive for Time Machine. Once I'm sure that I will not have to use the older drive to restore from, I then format it to use for something else or throw it away if it's outmoded.

Thanks Chscag - that was kind of my feeling but just wanted some experienced advice - hope that the new Thunderbolt connection does a better job at staying attached - have their same USB drive doing some CCC backups - Dave :)
 
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Well, today I received the new OWC external HD w/ Thunderbolt (TB) cable - just used Disk Utility to format as Mac OS extended, plugged into the back of our iMac, and setup Time Machine to do an initial backup (and stopped the BU to my USB Seagate HD).

An interesting observation that I cannot explain - in the past using the USB connection, a small triangle would appear in the top menu item to indicate the BU was occurring, and if I opened Finder the mounted HD would show a revolving wheel icon.

With this TB HD, I see the little triangle in the top menu icon (see pic below w/ arrow) and the backup shows progress, however, when I open Finder, the mounted OWC HD named iMac_TM (other pic and arrow) does not show a spinning progress icon - is this just a difference of behavior between these different connections or is something wrong? Thanks for any advice. Dave :)
.

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ADDENDUM to my post above - I've been watching the TM backups on this new TB OWC drive and the 'revolving arrows' are now appearing - so not a problem. Dave :)
 

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