External Thunderbolt 3 SSD good as internal SSD?

psymac

macrumors 6502a
Original poster
Jul 17, 2002
523
125
Can't wait for the updated Mac Mini, if it ever ships, so will go to a new 27" iMac. Those with just a HD or fusion HD are easily available and often on sale, unlike the SSD models. Wondering then if an Thunderbolt 3 connected external SSD would be as fast or nearly so as an internal SSD, and if cost effective. If so, can it be just a standard SSD in a Thunderbolt enclosure or is there a special T3 SSD?
 

ajf.350d

macrumors member
Nov 23, 2010
55
10
Worcestershire, UK
I would be interested to know this as well.
On paper, the Thunderbolt ports have more than enough bandwidth to be as fast as internal.
Like you, frustrating to see the SSD model iMacs (especially 512Gb) seem to always be on several week leadtime.
Also useful if it works to be able to add larger sizes cheaply (relative to Apple!).
 
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kschendel

macrumors 65816
Dec 9, 2014
1,054
332
The iMac internal SSD's aren't SATA, they are high speed PCIe devices. I don't think that there is any theoretical reason that an outboard Tbolt-3 enclosure couldn't drive a PCIe SSD, and in fact such things may exist for all I know, but I doubt that they would be cheap. If by "standard" SSD you mean a SATA drive, regardless of form factor, it's not going to be as fast as the iMac internal drive no matter what you connect it with.

That's considering single drives. I would expect that most external Thunderbolt enclosures with claims to speed would have an internal RAID controller and run multiple SSD's striped to get more speed.
 
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psymac

macrumors 6502a
Original poster
Jul 17, 2002
523
125
If by "standard" SSD you mean a SATA drive, regardless of form factor, it's not going to be as fast as the iMac internal drive no matter what you connect it with.
But at least significantly faster than a fusion hard drive right?
 
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xWhiplash

macrumors 68000
Oct 21, 2009
1,916
795
But at least significantly faster than a fusion hard drive right?
Definitely. Depending on the enclosure, you can probably get a constant 450 MB/s read and write out of it for all files on the drive.
 
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EugW

macrumors G3
Jun 18, 2017
8,114
5,461
I would be interested to know this as well.
On paper, the Thunderbolt ports have more than enough bandwidth to be as fast as internal.
Like you, frustrating to see the SSD model iMacs (especially 512Gb) seem to always be on several week leadtime.
Also useful if it works to be able to add larger sizes cheaply (relative to Apple!).
Order date of my 1 TB SSD iMac to my delivery date to my home was less than a week. ;)
 
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kschendel

macrumors 65816
Dec 9, 2014
1,054
332
But at least significantly faster than a fusion hard drive right?
Well, maybe. One of the things many people don't like about fusion drives is that it's hard to say anything absolute about their performance. If you manage to hit the SSD part of a fusion, it will likely out-perform the external SATA because again, as far as I know, the internal SSD is faster. If you have to deal with the hard disk part, any decent external SATA SSD should be run away with it.
 
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rjsounds

macrumors member
Jul 3, 2017
69
26
Order date of my 1 TB SSD iMac to my delivery date to my home was less than a week. ;)
You're lucky! I regret buying the 512SSD... almost 5 weeks and counting, still don't have it yet :(
 
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