Using External SSD as Primary Disk on iMac

lugesm

macrumors 6502a
Original poster
Sep 7, 2007
572
9
Running a EXTERNAL Samsung 840 PRO, 512GB SSD via Thunderbolt as my primary system disk for a 27" iMac.

Works great. Fast FAST F A S T

Question: I would like to use my internal 1TB HDD as the Time Machine disk. If my SSD should fail, can I totally rebuild my system without data loss from the internal 1TB HDD running Time Machine? I have only used Time Machine in the past for restoring individual files; not sure it can boot and run as primary drive when it has been running as Time Machine.

Thanks for your help.
 

Mikebike125

macrumors 6502
Mar 25, 2007
381
10
Please excuse my lack of computer experience as I ask this question. Could you explain or point me to how I could make a setup like yours where the whole operating system is on an external drive? I am running out of space on my 2007 imac and would like to do what you are trying to do. I don't mean to hijack your thread but I am just so interested in what you have done.

Thanks
 

joe-h2o

macrumors 6502a
Jun 24, 2012
997
443
Please excuse my lack of computer experience as I ask this question. Could you explain or point me to how I could make a setup like yours where the whole operating system is on an external drive? I am running out of space on my 2007 imac and would like to do what you are trying to do. I don't mean to hijack your thread but I am just so interested in what you have done.

Thanks
The 2007 iMac don't have a Thunderbolt (or USB3) port, so you can do this but you'll be bottlenecked for speed. Your best bet if you must do it is over firewire, but the system will be slowed by the speed of the firewire bus.

To do it just hook a drive up as normal and select it as the destination drive when installing OS X (format it if necessary, use Mac OS Extended (Journalled) ).

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Running a EXTERNAL Samsung 840 PRO, 512GB SSD via Thunderbolt as my primary system disk for a 27" iMac.

Works great. Fast FAST F A S T

Question: I would like to use my internal 1TB HDD as the Time Machine disk. If my SSD should fail, can I totally rebuild my system without data loss from the internal 1TB HDD running Time Machine? I have only used Time Machine in the past for restoring individual files; not sure it can boot and run as primary drive when it has been running as Time Machine.

Thanks for your help.
Yes, you could do this. There's nothing stopping you using your internal HD as a Time Machine volume - you can use any volume that isn't your active boot volume, whether it it internal or external. There are Mac Pro users, for example, who have their OS on the drive in bay 1 and the time machine backup on another internal drive in bay 2 etc.

The only downside to using your internal drive on the iMac as the TM drive is that if you need to physically get at it (eg, if you were swapping out the iMac if it has a hardware fault) it's inside the machine so it's not as easy to just put to the side during a hardware change as an external one would be.

In terms of the actual function of Time Machine though, no problems at all.
 

lugesm

macrumors 6502a
Original poster
Sep 7, 2007
572
9
Could you explain or point me to how I could make a setup like yours where the whole operating system is on an external drive? I am running out of space on my 2007 imac

Thanks
Unfortunately, your 2007 iMac does not have a Thunderbolt connection which is essential for the necessary transfer speeds. I know of no practical way to use an external PRIMARY drive with your machine; even your FireWire connection is too slow to use as a connection to an external primary drive.
 

Nuke61

macrumors 6502
Jan 18, 2013
325
0
Columbia, SC
Running a EXTERNAL Samsung 840 PRO, 512GB SSD via Thunderbolt as my primary system disk for a 27" iMac.
Interesting, because I've read in the past that 512GB SSDs used too much power to be used as a boot drive... maybe the 840 Pro uses less power than most. I'm now using a 256GB 840 Pro as my boot disk, with my internal Fusion drive as a backup. Not really much difference in speed (FAST) but I figured, why not?

Question: I would like to use my internal 1TB HDD as the Time Machine disk. If my SSD should fail, can I totally rebuild my system without data loss from the internal 1TB HDD running Time Machine? I have only used Time Machine in the past for restoring individual files; not sure it can boot and run as primary drive when it has been running as Time Machine.
You can rebuild from the internal HDD that's being used as a Time Machine backup drive, but AFAIK, it is not directly bootable.

What *I* do is use SuperDuper! (but Carbon Copy Cloner will work too) to make BOOTABLE backups of my SSD to:
1) My internal Fusion drive
2) Another external Thunderbolt SSD
3) An external USB 3 SSD
and the backups are done automatically on a schedule.

I have more backups, but those 3 are directly bootable.
 

lugesm

macrumors 6502a
Original poster
Sep 7, 2007
572
9
Interesting, because I've read in the past that 512GB SSDs used too much power to be used as a boot drive... maybe the 840 Pro uses less power than most. I'm now using a 256GB 840 Pro as my boot disk, with my internal Fusion drive as a backup. Not really much difference in speed (FAST) but I figured, why not?
Can you reference the source of the question of power required by 512GB SSDs ? I am a little concerned that I might be right on the edge and not know it.
 

Bear

macrumors G3
Jul 23, 2002
8,089
4
Sol III - Terra
Interesting, because I've read in the past that 512GB SSDs used too much power to be used as a boot drive... maybe the 840 Pro uses less power than most.
...
This sounds like an odd claim unless they were trying to power the SSD from the Thunderbolt bus. In which case it should be in a case with it's own power supply.
 

CoinOP

macrumors member
May 11, 2013
52
0
Amsterdam
Could you guys please tell me how long the boottime is? I have a 840 256 with a thunderbolt adapter from Seagate. Boottime is 32 seconds....
 

lugesm

macrumors 6502a
Original poster
Sep 7, 2007
572
9
Yes, it was for a bus powered SSD.
Actually, my system uses the Samsung 840 Pro 512GB SSD running on the Seagate Thunderbolt adapter with an Apple 18" Thunderbolt cable to the iMac. I am not sure if I might be on the edge here, but the Samsung runs pretty cool. Anyone know the current limits for Thunderbolt ?

Found these power specs published by one reviewer.
Active Power Use: 0.068W (down from 0.24W for 830 Series)
Idle Power Use: 0.042W (down from 0.14W for 830 Series)


Samsung's published power requirement for the 512
gb 840 Pro is 0.15 watts or 30ma @ 5V.



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Could you guys please tell me how long the boottime is? I have a 840 256 with a thunderbolt adapter from Seagate. Boottime is 32 seconds....
To qualify: My system is . . . mid-2011 27" iMac with 3.4Ghz Core i7 and 16GB memory. I described the external SSD configuration above.

My boot milestones are consistently:
Zero to the appearance of the gray apple = 13 seconds
Gray apple to full desktop = 6 seconds
The cursor is frozen for another 10 seconds.
Total time = 13 + 6 + 10 or 29 seconds.

I ran the same tests with an older Crucial 256 GB SSD (in theory, slower) and found exactly the same numbers, so factors other than SSD speed are probably setting the speed limits.
 
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jediDev

macrumors regular
Jun 13, 2012
118
0
This sounds like an odd claim unless they were trying to power the SSD from the Thunderbolt bus. In which case it should be in a case with it's own power supply.
i boot with buffalo's ministation thunderbolt, totally bus powered, 500 GB samsung ssd, and have never had a problem with the power.

flcikering when using the imac in target display mode is another problem, however. but in testing i've pretty much ruled out the external ssd.
 

lugesm

macrumors 6502a
Original poster
Sep 7, 2007
572
9
A small part is magnetic. What i did was attach the ssd to an old metal laptop holder to hold it in place.
A spacer (about 3mm) is needed between the rear of the SST and the Seagate Thunderbolt adapter bed. Such a spacer holds the SSD in good alignment with the connector on the Thunderbolt adapter.

I assume you used a thick, magnetic disk in that position. Such a disk would perform the double function of holding the SSD in position and properly spacing it from the adapter bed.

Good idea, as long as the strong magnetic field from the disk does not in some way interfere with the operation. :eek:
 

CoinOP

macrumors member
May 11, 2013
52
0
Amsterdam
I used an open? plastic spacer for the alignement. Just a small part of the adapter is magnetic and without the metal plate it has no effect. I would worry more with a standard drive:).
 

Che Castro

macrumors 603
May 21, 2009
5,671
511
Damn $100 for that adapter and then another $100 for the ssd
I'm just gonna man up and install it myself inside
 

lugesm

macrumors 6502a
Original poster
Sep 7, 2007
572
9
Damn $100 for that adapter and then another $100 for the ssd
I'm just gonna man up and install it myself inside
The Thunderbolt adapter is about $100 (The SSD is more than $100). The 0.5M Thunderbolt cable is about $29.

So the cost of this external SSD operating as the primary drive is about $130 over the cost of having installed the SSD internally.
This, to me, is justifiable; as it keeps all of my options open and runs very little implementation risk . . . . not to mention warranty issues.

Your iMac warranty will be voided if you open the unit.
 
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CoinOP

macrumors member
May 11, 2013
52
0
Amsterdam
The Thunderbolt adapter is about $100 (The SSD is more than $100). The 0.5M Thunderbolt cable is about $29.

So the cost of this external SSD operating as the primary drive is about $130 over the cost of having installed the SSD internally.
This, to me, is justifiable; as it keeps all of my options open and runs very little implementation risk . . . . not to mention warranty issues.

Your iMac warranty will be voided if you open the unit.
I already had an ssd. I went the external round because I didn't want to bring in a brand new Imac and getting it back scratched, waiting 5 to 7 days and pay 80€ an hour. This way my Imac is pristine and I have options open.....Peace of mind alone worth the 130 bucks.
 

Nuke61

macrumors 6502
Jan 18, 2013
325
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Columbia, SC
Can you reference the source of the question of power required by 512GB SSDs ? I am a little concerned that I might be right on the edge and not know it.
I couldn't find any sources on MacRumors that talk about a possible issue with Thunderbolt SSDs as boot drives when powered only by the Thunderbolt bus, but I did see the reference here first, and then went looking elsewhere for possible reasons and/or solutions. Here's one such link: http://wolfgangtechnology.blogspot.co.at/2012/06/mac-with-seagate-thunderbolt-adapter.html where a *powered* Thunderbolt housing works fine, but a non-powered Thunderbolt connection has issues.
 

lugesm

macrumors 6502a
Original poster
Sep 7, 2007
572
9
I couldn't find any sources on MacRumors that talk about a possible issue with Thunderbolt SSDs as boot drives when powered only by the Thunderbolt bus, but I did see the reference here first, and then went looking elsewhere for possible reasons and/or solutions. Here's one such link: http://wolfgangtechnology.blogspot.co.at/2012/06/mac-with-seagate-thunderbolt-adapter.html where a *powered* Thunderbolt housing works fine, but a non-powered Thunderbolt connection has issues.
Good article. Thank you for following up with the reference article.

Notes:
1. The article is about a year old.
2. The author used Samsung 830 series 512GB SSD.
The Samsung 840 Pro uses significantly less power than the 830 series.
3. The author was using a MBP with Thunderbolt, not an iMac with Thunderbolt
It is possible the iMac provides more current than the MBP.

Another observation: I have successfully run (on my iMac) this same Seagate Thunderbolt adapter with conventional HDDs from Seagate up to 750GB without issue.
 
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vtyler98

macrumors member
Jul 27, 2011
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