Advice upgrading PCIe and SATA drives on 2017 iMac

Woodlandjustin

macrumors member
Original poster
Jan 21, 2007
38
1
Hi!
I have a 2017 27 inch iMac (EMC 3070) with a 1TB fusion drive. I'm wanting to upgrade the storage, and thinking:
Upgrade SATA III to:
Crucial MX500 2TB (3D NAND, SATA, 2.5 Inch, Internal SSD)

Upgrade the PCIe to:
Samsung 970 EVO 250GB M.2-2280 SSD

Does this seem a good plan? I reckon I can put the OS and apps on the faster 970 drive this way.
Is there any problem with heat from the 970?

Also I'm in London, anyone know a good priced and reliable service for getting this done? I'm assuming I might be saving money if I buy the drives online and just pay someone to install them, and install the OS. Anyone have advice on best place to buy? Amazon, ebay (safe?)?

Also, anyone know how much SSD the 1TB fusion drive has? I figure it's worth upgrading that to the 250GB, since it's only around £70, but if anyone has better suggestions or thinks that's not worth the bother...?

Many thanks!
 
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Neo_Hunt

macrumors newbie
Jan 16, 2017
27
7
Hi there!

I'd go for at least 512GB for the PCIe SSD.
But since you have the 32GB one, 256GB should give a noticeable performance leap.
https://en.wikipedia.org/wiki/Fusion_Drive

I have a Late 2013 iMac with a 512GB Apple PCIe and a 1TB 860 EVO SATA setup as one 1.5TB Fusion Drive.

If I were you, I'd give a look on eBay and other online shops for the original Apple SSD.
In your case it would be the Samsung SSPOLARIS, the first - larger than 32GB - Apple NVMe Drive.
I've read people with adaptors and 3rd party SSDs can get Sleep and Hibernation problems in a good thread around.

Beetstech sells this original SSDs, but they are expensive (link):
https://beetstech.com/product/sspolaris-ssd-256gb-512gb-1tb-2tb
I paid half price for my 512GB UAX SSD (original from the Trash Can Mac Pro) on an US eBay listing.

It seems OWC has started selling what is supposed to be a 100% compatible SSD, no adapter needed.
But I am not sure whether Sleep/Hibernation problems do exist. They are discussing it on another thread (link):
https://forums.macrumors.com/thread...r-macbook-air-and-macbook-pro-models.2178148/

Those are in theory compatible with the same slot, but were not tested yet for OWC to list as iMac compatible.
https://eshop.macsales.com/shop/ssd/owc/aura-pro-x2

I really like my "clean" setup with two internal SSDs, one original from Apple, and no external dongle on my iMac.
But I think a lot of people around might try to tell you to go the external route, which is simpler and cheaper.

Cheers!
 
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mikehalloran

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Oct 14, 2018
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Forget 256GB, Get a 2TB 970 EVO

Throw away the HDD. If you need additional storage, put an SATA III SSD in there. A 2TB Crucial MX500 is less than $240. Your iMac won’t know the difference between that and the 860 EVO.
 

Woodlandjustin

macrumors member
Original poster
Jan 21, 2007
38
1
I'd go for at least 512GB for the PCIe SSD.
I was thinking about that but could not figure out what the advantage would be. I heard that faster PCIe is a good place to put the OS and applications. Is that right? That won't take much space - my applications folder right now is less than 38GB. Apart from that, I honestly don't know if putting my instrument library (used with a DAW for making music) would behave any differently if it were on that vs SATA connection SSD, does anyone here know if that would make a real difference? If not, then no point! But even if so, my instrument library is more than 500GB. So just for the library I prefer to have at least 1TB.

So what if I only have less than 38GB of apps, and I'd have to create two separate instrument libraries (hassle for navigation when in the DAW I would expect) just to put *some* of the library on that disk, then what's going to be actually noticeably useful to put on this super-fast PCIe drive? What would make it worth it?

I've read people with adaptors and 3rd party SSDs can get Sleep and Hibernation problems. There is a good thread around.
I heard that was an issue only for pre-2017 iMacs, thus not for mine. But please correct me if I'm wrong!
And thanks for the tips on places to buy drives!

If you need additional storage, put an SATA III SSD in there. A 2TB Crucial MX500 is less than $240. Your iMac won’t know the difference between that and the 860 EVO.
Any reason you are suggesting only going with SATA, and not adding any PCIe drive?
 

Neo_Hunt

macrumors newbie
Jan 16, 2017
27
7
I think "worth it" is generally a subjective term.
Indeed, you are the best person to decide what is worth it for you, of course.

That being said, I did to my old iMac the same thing I'd probably do to an eventual new one...
Get the highest capacity original PCIe Apple SSD possible and the highest capacity SATA SSD as well.
In fact, the day I give myself a 4K 2017 or 2019 iMac I'll make sure it's the Fusion Drive model so I can upgrade it.

Why not only 1 drive you may ask?
Well... I like the idea of upgrading the iMac myself, even taking the chance to upgrade RAM and CPU as well.
In hindsight I think on my case a 2TB SATA could've made more sense since the actual speed is almost the same.
But I may upgrade it in the future, say for a 4TB SATA QLC. Then even the "slow" PCIe 2.0 x2 Blade SSD would help.
Also, the 1TB Apple SSD was too expensive, as were some NVMe's which for the PCIe 2x2 case is simply to "worth it".
;ˆ)


About the eventual sleep problems, I think they're related to Macs which were never populated with an Apple SSD.
In your case you are probably not going to have problems. But we can't be sure for any eventual future update.
I prefer the Apple original SSDs not to have the possibility of any Firmware/BootROM problems in the future.

For now, you could give yourself the highest capacity SSPOLARIS drive and go external for your DAW files.
When the time comes, if you're still ok with your 2017 iMac, you can then reopen it just to upgrade the SATA Drive.
I suppose in the near future QLC SSD drives (Samsung QVO) will pull the price per TB down, closer to platters' prices.

And don't forget that for your 2017 iMac the PCIe 3.0 x4 interface gives you from 4 to 7-fold the SATA bandwidth.
Be it an Apple original SSD or a 3rd party one, the PCIe Blade SSD will give you a "better future".
Also remember for SSDs, higher the capacity, higher the performance and higher the endurance.
 
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Zdigital2015

macrumors 68030
Jul 14, 2015
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East Coast, United States
Hi!
I have a 2017 27 inch iMac (EMC 3070) with a 1TB fusion drive. I'm wanting to upgrade the storage, and thinking:
Upgrade SATA III to:
Crucial MX500 2TB (3D NAND, SATA, 2.5 Inch, Internal SSD)

Upgrade the PCIe to:
Samsung 970 EVO 250GB M.2-2280 SSD

Does this seem a good plan? I reckon I can put the OS and apps on the faster 970 drive this way.
Is there any problem with heat from the 970?

Also I'm in London, anyone know a good priced and reliable service for getting this done? I'm assuming I might be saving money if I buy the drives online and just pay someone to install them, and install the OS. Anyone have advice on best place to buy? Amazon, ebay (safe?)?

Also, anyone know how much SSD the 1TB fusion drive has? I figure it's worth upgrading that to the 250GB, since it's only around £70, but if anyone has better suggestions or thinks that's not worth the bother...?

Many thanks!
Your 2017 iMac has a 1TB Fusion with 32GB of PCIe SSD storage in a slot on the motherboard and a 3.5" 1TB SSD mounted on the chassis to the left of the motherboard. I am not keen on the third party SSD replacements, because you may encounter issues with updating your iMac's firmware in the future.

If performance is lackluster, you can replace the 32GB SSPOLARIS SSD with a 128GB SSDPOLARIS (Apple OEM) or a larger size and either keep it separate or rebuild the Fusion Drive. If you keep it separate, I would recommend at least the 256GB or 512GB SSDPOLARIS and have it replaced by an Apple authorized shop if you happen to still be under warranty.

If you want to take the 1TB HDD out, I would replace it with a Samsung 860 EVO or PRO. I have one Crucial MX300 1TB and it does well enough, but it is in a Late 2011 MacBook Pro which is 10 screws and its accessible.

Otherwise, you might be better served by simply getting some USB 3 external storage (Samsung T5 or SanDisk Extreme Portable SSD) and some more DRAM, depending on whether or not you have already updated that earlier as opposed to having someone open your iMac up and start replacing things. It would certainly be cheaper and less down time.

Good luck!
 

mikehalloran

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Oct 14, 2018
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It seems OWC has just launched the Aura N, which supposedly "fits" perfectly 2013 Macs and theirs PCIe x2 slots.
https://appleinsider.com/articles/19/05/14/owc-launches-aura-n-internal-upgrade-ssds-for-macs
https://eshop.macsales.com/shop/ssd/owc/aura-n
Yes, NVMe 2.

These will be slower than the NVMe 3 x4 blades in 2017–2019 iMacs and 2015–later MacBook Pros. The 2015 iMac has a PCie 3 x4 bus but the slower NVMe x2 chip.

OWC does not offer an NVMe 3 x4 blade for the iMac. When you look at the late model iMacs, they only offer an SSD for the SATA III bus.
https://eshop.macsales.com/shop/ssd/owc/imac-27-inch/late-2013-2017

Interestingly, they do offer the NVMe 3 x4 blade for the 2013–2015 MacBook Pro, the Aura Pro X2.
https://eshop.macsales.com/shop/ssd/owc/macbook-pro-retina-display/2013-2014-2015
This should work in the iMac but I don't know why OWC doesn't offer it unless there are heat issues. I ordered one last week for a 2015 iMac i7 but OWC took too long to ship and I had to return it—I used a 970 EVO instead and it went well.
 

Neo_Hunt

macrumors newbie
Jan 16, 2017
27
7
These will be slower than the NVMe 3 x4 blades in 2017–2019 iMacs and 2015–later MacBook Pros. The 2015 iMac has a PCie 3 x4 bus but the slower NVMe x2 chip.
I suppose performance wise they would be identical on an old PCIe 2 x2 Late 2013 iMac. It seems a better value.

Interestingly, they do offer the NVMe 3 x4 blade for the 2013–2015 MacBook Pro, the Aura Pro X2.
https://eshop.macsales.com/shop/ssd/owc/macbook-pro-retina-display/2013-2014-2015
This should work in the iMac but I don't know why OWC doesn't offer it unless there are heat issues.
I think I read on the Aura Pro X2 thread that they are still validating its use on the iMac.
I suppose MacSales have not a lot of opened iMacs lying around.
 

mikehalloran

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Oct 14, 2018
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I think I read on the Aura Pro X2 thread that they are still validating its use on the iMac.
I suppose MacSales have not a lot of opened iMacs lying around.
Actually, they do repairs and modifications in-house.

I'm guessing the real issue is heat. There's no space for a heat sink behind the right speaker. OWC normally uses Intel chips and it would surprise me if these were any different.

So, as long as they can't guaranty that no one will have problems, they refuse to recommend them. This makes perfect sense.
 

mdelrossi

macrumors regular
Jun 22, 2005
116
67
Photographer here,
Since you have an instrument library, and working with a DAW, I'd suggest getting rid of both and going the route I did if you can. Everything is faster, since you have a 2017 the PCIE Blade should be at least twice as fast as mine.
All in, I spent aprox $350 USD, worth it to me.


My specs:
Late 2014 27" 5K i7 4790k 295x with 3 TB fusion, Mojave 10.14.5 ( also worked on an earlier version of Mojave that used HFS+)
Just replaced the Seagate 3tb with a 2TB ssd, and also replaced the 128GB Pcie blade with a intel 1TB + adapter.
Intel SSD 660p : https://www.bhphotovideo.com/c/product/1437035-REG/intel_ssdpeknw010t8x1_660p_1tb_ssd_pci.html

I booted from the T5 I had been booting from for the past year or so. then installed Mojave 10.14.4 on it.
Migrated all my info and files from the T5 to the SSD blade.
It booted up just fine, then updated to mojave 10.14.5 via software update.

After doing this, I regret not getting the 2TB blade.

Flawless. Goes to sleep, wakes up no terminal command.
 

Neo_Hunt

macrumors newbie
Jan 16, 2017
27
7
Actually, they do repairs and modifications in-house.

I'm guessing the real issue is heat. There's no space for a heat sink behind the right speaker. OWC normally uses Intel chips and it would surprise me if these were any different.

So, as long as they can't guaranty that no one will have problems, they refuse to recommend them. This makes perfect sense.
Did not know that. Great tech answer! Thanks! It makes perfect sense, but...
... OWC says "Consumes less power and runs cooler for longer battery life"... Go figure!
https://www.owcdigital.com/products/aura-n

Photographer here...
Just replaced the Seagate 3tb with a 2TB ssd, and also replaced the 128GB Pcie blade with a intel 1TB + adapter.
Intel SSD 660p
One eventual problem I see with the Intel 660p is that it's a QLC Drive, not the best one for endurance.
I'd not recommend a QLC Drive for the "Fast SSD side" of a Fusion Volume.
At least it'd be advisable to get the largest possible, 2TB as you say...

If not using a Fusion Volume, I suppose it's more than ok, since it must be much better than the 1st TLC Drives...
I'd been using an old Samsung 840 (the original, not EVO) on my previous 2007 iMac and have never had an issue!
 

mdelrossi

macrumors regular
Jun 22, 2005
116
67
One eventual problem I see with the Intel 660p is that it's a QLC Drive, not the best one for endurance.
I'd not recommend a QLC Drive for the "Fast SSD side" of a Fusion Volume.
At least it'd be advisable to get the largest possible, 2TB as you say...

If not using a Fusion Volume, I suppose it's more than ok, since it must be much better than the 1st TLC Drives...
I'd been using an old Samsung 840 (the original, not EVO) on my previous 2007 iMac and have never had an issue!
Good point,
I researched it and found this practical explanation on an amazon review "Unless you have a really write intensive work load (like writing 100+GB every day for five years), then I highly doubt you'll ever come close to hitting that limit."

So in my case my machine will be 10+ years old and replacing the drive then won't be an issue, assuming the rest of the machine is still working.
For $100 it was worthwhile.

mdr
 
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mikehalloran

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Oct 14, 2018
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One eventual problem I see with the Intel 660p is that it's a QLC Drive, not the best one for endurance.
I'd not recommend a QLC Drive for the "Fast SSD side" of a Fusion Volume.
At least it'd be advisable to get the largest possible, 2TB as you say...

If not using a Fusion Volume, I suppose it's more than ok, since it must be much better than the 1st TLC Drives...
Although I agree, if already done and working ok, I would leave it alone. If it works, it works.
I'd been using an old Samsung 840 (the original, not EVO) on my previous 2007 iMac and have never had an issue!
Good for you. With the firmware issues those had — but you know about those, I figure. Again, if it works... and, if not, throwing in something newer is a piece of cake on any pre-2012 iMac.
 

Neo_Hunt

macrumors newbie
Jan 16, 2017
27
7
Although I agree, if already done and working ok, I would leave it alone. If it works, it works.
I completely agree! If it's working there is no need to try breaking the iMac display once more ;ˆP
For normal use, the 660p must be a great value! My concern is related to an eventual Fusion Drive "cache like" use.

Good for you. With the firmware issues those had — but you know about those, I figure. Again, if it works... and, if not, throwing in something newer is a piece of cake on any pre-2012 iMac.
Regarding the Original 840, I think it was a mix of luck and research.
I always used the Trim command, since the old "Trim Enabler Utility" to the new Yosemite's "trimforce".
I've also always installed Samsung firmware updates the week they were launched, including most recent one.

Still, I think most of the problems were reported on the 840 EVO (19nm TLC), not the older 21nm TLC "vanilla" 840.
 
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Woodlandjustin

macrumors member
Original poster
Jan 21, 2007
38
1
If performance is lackluster, you can replace the 32GB SSPOLARIS SSD with a 128GB SSDPOLARIS (Apple OEM) or a larger size and either keep it separate or rebuild the Fusion Drive. If you keep it separate, I would recommend at least the 256GB or 512GB SSDPOLARIS and have it replaced by an Apple authorized shop if you happen to still be under warranty.
I'm trying to work out what the actual difference would be if making that bigger. I also don't understand the difference of whether it's left set up as a fusion drive, or made into two separate drives. Or how to make either happen (if I just replace both and load the OS to the PCIe drive, will it remain automatically as a fusion drive?)

For example, the 32GB is not enough for my whole applications folder. So I could just have the OS on it? Does this apply also to whether fusion or not? And, assuming the OS being on the faster drive makes things faster somehow, what else is worth putting on that drive that would also make a difference? Applications - makes a difference? That would push me over the 32GB range, but then the next step up from that would be to put my instrument library on it, for which I basically would need 1TB - that's expensive! But I could consider it. Also, any problems with heat? Perhaps larger drive means more heat? and if so is this an issue for let's say EVO 970 1TB? Someone has mentioned the Intel 760p, which might get less hot? Seems about the same price here. I know it might to be quite as good as the EVO 970 but they seem both so much better than SATA, if one has less heat maybe that is more relevant? N.B. I don't like fan noise to running quieter is a real plus for me.

Also, I have only 8GB of RAM. I plan to get 32GB more bringing it to 40GB. I think I read somewhere that the small 32GB of PCIe on the 1TB fusion drive is not enough when you increase the RAM like that, something about some applications freezing or something? Is that true? If so, I will definitely need to make that drive bigger, but otherwise, I am not hearing that it will make much difference at all for working in a DAW, compared to the EVO 860 or Crucial MX500 on SATA.

It seems OWC has just launched the Aura N, which supposedly "fits" perfectly 2013 Macs and theirs PCIe x2 slots.
https://appleinsider.com/articles/19/05/14/owc-launches-aura-n-internal-upgrade-ssds-for-macs
https://eshop.macsales.com/shop/ssd/owc/aura-n
Unfortunately there's nothing there (confirmed) for using in iMac 2017.

My specs:
Late 2014 27" 5K i7 4790k 295x with 3 TB fusion, Mojave 10.14.5 ( also worked on an earlier version of Mojave that used HFS+)
Just replaced the Seagate 3tb with a 2TB ssd, and also replaced the 128GB Pcie blade with a intel 1TB + adapter.
Intel SSD 660p : https://www.bhphotovideo.com/c/product/1437035-REG/intel_ssdpeknw010t8x1_660p_1tb_ssd_pci.html

I booted from the T5 I had been booting from for the past year or so. then installed Mojave 10.14.4 on it.
Migrated all my info and files from the T5 to the SSD blade.
It booted up just fine, then updated to mojave 10.14.5 via software update.

After doing this, I regret not getting the 2TB blade.
Er 1TB blade no? Or did I misunderstand? How did you handle the two drives - did you split them?

If not using a Fusion Volume, I suppose it's more than ok, since it must be much better than the 1st TLC Drives...
Anyone want to chip in about this fusion vs. non-fusion topic?

Thanks for all the help guys!
 
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Woodlandjustin

macrumors member
Original poster
Jan 21, 2007
38
1
Regarding PCIe:
Also, any problems with heat? Perhaps larger drive means more heat? and if so is this an issue for let's say EVO 970 1TB? Someone has mentioned the Intel 760p, which might get less hot? Seems about the same price here. I know it might to be quite as good as the EVO 970 but they seem both so much better than SATA, if one has less heat maybe that is more relevant? N.B. I don't like fan noise to running quieter is a real plus for me.
I've also just been reading good things about the ADATA XPG SX8200 Pro 1TB, and that that is meant to run a lot cooler than the EVO 970. Anyone have anything to say about that? Sounds like that might be the best option....?
 
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Neo_Hunt

macrumors newbie
Jan 16, 2017
27
7
Unfortunately there's nothing there (confirmed) for using in iMac 2017.
I think the OWC Aura N would be a good idea for 2013 Macs with PCIe 2.0 x2 Slots.
For your 2017 iMac, Apple's SSPOLARIS is the best one. From OWC, I suppose the Aura Pro X2 is the best.
The OWC drives DON'T need adapters. Unfortunately, as of today, they have yet to be iMac "certified", I suppose.
 

Woodlandjustin

macrumors member
Original poster
Jan 21, 2007
38
1
I think the OWC Aura N would be a good idea for 2013 Macs with PCIe 2.0 x2 Slots.
For your 2017 iMac, Apple's SSPOLARIS is the best one. From OWC, I suppose the Aura Pro X2 is the best.
The OWC drives DON'T need adapters. Unfortunately, as of today, they have yet to be iMac "certified", I suppose.
When I've seen Apple's SSPOLARIS online they are hundreds of dollars/pounds more than the other drives, which is why I have avoided them. If you have a competitive source however, I'd consider it!

Regarding the OWC Aura N, prices seem to vary really wildly! On mrmemory.co.uk, the 1TB upgrade kit for that costs £803.99! Cheapest I could find was on www.owcshop.eu, including VAT to UK would be about £226 just for the drive, or £289 for the kit (plus shipping presumably). I don't see any 'pro x2', or did you mean to buy two of them?

Anyway, with the:
-Samsung 970 EVO 1 TB at around £190, and the
-ADATA XPG SX8200 Pro 1TB at around £158,
I don't see the need to spend significantly more money for a drive that doesn't last as long (I assume from the mere 3 year Limited Warranty vs. I think 5 years for those others) especially when it isn't sure there are no issues with it on the iMac 2017.
 

Neo_Hunt

macrumors newbie
Jan 16, 2017
27
7
Prices vary from time to time and by region. Buy the one you feel is best for you.
Looking at eBay's listings, the SSPOLARIS are too expensive indeed.
My UAX and some UBX are much more reasonably priced!
But those are PCIe AHCI, not NVMe.

For the 3rd time, maybe my English is really bad, the Aura N would be best for OLDER Macs! ;ˆ)
It's only PCIe x2 (not x4) and has a maximum read rate of 1.6Gbps.

On my first post up above there is a link to the Aura Pro X2's thread, and also for its page at macsales.com.
It should be the recommended one for newer Macs such as the 2017 iMac with PCIe 3.0 x4.
In the end the Samsung 970 might be a better idea, if one does not mind adapters!

Apple OEM Blade SSDs are generally MLC, and should last longer then the TLC drives mention in the thread.
On the other hand, 3D TLC has come a long way and it probably has more than enough endurance.
 
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Woodlandjustin

macrumors member
Original poster
Jan 21, 2007
38
1
For the 3rd time, maybe my English is really bad, the Aura N would be best for OLDER Macs! ;ˆ)
It's only PCIe x2 (not x4) and has a maximum read rate of 1.6Gbps.

On my first post up above there is a link to the Aura Pro X2's thread, and also for its page at macsales.com.
It should be the recommended one for newer Macs such as the 2017 iMac with PCIe 3.0 x4.
Blade upgrade: 32GB Blade -> 2TB Samsung 970 EVO NVMe SSD
Ah sorry for any misunderstanding. Yeah I've found the Aura Pro X2 on the www.owcshop.eu site now. It's more than £288! I found it one other place at £235.49, but still, that's so much more than the Samsung 970 EVO 1 TB at around £190; and the ADATA XPG SX8200 Pro 1TB at around £158, that I can't see how I could justify that, if the performance is basically similar, you know? Doesn't seem enough of a difference in performance from what I can hear at least, for such a quantum leap in price.

I'm just curious how the ADATA and EVO compare. If anyone has a sense of that, I would love to hear about it! I feel like I've narrowed it down to these two drives. The one I've heard most infrequently talked about is the ADATA, though what I have heard about it has been very good. And if it is cooler and cheaper, but apart from that basically similar, then that would seem more of an advantage than a tiny bit more speed, which might turn out to be more of a theoretical more than actually experienced difference, at that point. Would love to hear about real experiences though! I'm still very new to this.
 

randyharris

macrumors regular
Jul 10, 2006
134
2
I've had my 2017 iMac with 16GB of RAM and a 2TB Fusion drive since new. Just recently upgraded from 16GB to 64GB and am now thinking about a drive upgrade.

I currently have a 4TB external drive which I use for Time Machine.

Here is what I'm thinking would be pretty slick.

Swap out the 128GB blade SSD for a 2TB blade. Swap out the 2TB HDD for a 6TB HDD.

That lets me operate 100% off a super fast SSD, and then I'd partition the 6TB internal HDD, use 2TB as a clone drive, and use the 4TB partition for Time Machine.

My previous iMac's were really easy to crack open and swap out HDD for SSD, but these newer models are intimidating to get in there and make these changes.
 

Zdigital2015

macrumors 68030
Jul 14, 2015
2,534
2,989
East Coast, United States
I've had my 2017 iMac with 16GB of RAM and a 2TB Fusion drive since new. Just recently upgraded from 16GB to 64GB and am now thinking about a drive upgrade.

I currently have a 4TB external drive which I use for Time Machine.

Here is what I'm thinking would be pretty slick.

Swap out the 128GB blade SSD for a 2TB blade. Swap out the 2TB HDD for a 6TB HDD.

That lets me operate 100% off a super fast SSD, and then I'd partition the 6TB internal HDD, use 2TB as a clone drive, and use the 4TB partition for Time Machine.

My previous iMac's were really easy to crack open and swap out HDD for SSD, but these newer models are intimidating to get in there and make these changes.
Honestly, if you're going to take the time to open up the iMac and remove the logic board to put in a new PCIe blade, you should really consider adding a 2.5" SSD inside of the iMac and not spinning rust. A 3.5" HDD simply generates heat and will go bad sooner rather than later inside the iMac (~4 years). Install a 2TB Samsung 860 EVO (~$300) and use that as your clone drive. Less heat, longer life. Leave the Time Machine external on a USB connection. I only connect mine at intervals to get a backup so that it runs very little and keeps it around longer..

YMMV.
 
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