What's your definition of small files? In my case, the camera produces RAWs that are 30-50mb, and I really don't want to mess around with managing storage. I've been thinking over the idea of setting up my photo drive as a fusion drive, with a 128gb m2 on a lycom card or similar, given the photos I'm working on are almost always going to be the most recent ones imported, so they're afaik going to be on the ssd portion.
Weighing that against what I do if the machine dies, and I need to access the photos on a machine without a PCI slot. I can drop the spinning drive into an external case or similar, can you put the pcie m2 sticks in an external case, or only the sata ones?
For really small file, we usually talking about 4kB in size. Of course no photos will be that small nowadays. However, in my definition, most photos related job are dealing with small files (unless you are dealing with single multi hundred MB size photo).
I can put it like this.
30MB photo.
On a SSD that only with SATA II connection, loading time is <0.2s.
On a SSD that with 1500MB/s read performance, the loading time is <0.1s.
So, for human, there is practically no difference. Most of time spend on moving the mouse, click the correct file, etc. And we will feel that the file pop up straight away.
To make the difference, we need a GB file. e.g. 1GB file
For SATA II limiting SSD, loading time is 4s
For 1500MB/s PCIe SSD, loading time is <0.7s
For humans, there is significant difference, which is feeling like "have to wait" or "no need to wait".
So, in order to make us fell different, we need a file that clearly larger than 100MB.
Also, when dealing with photos, we usually dealing with hundreds or even thousands of photos. Even though the total size is large. However, most of the time we are just browsing through the thumbnails, but not really open / load all of them at once.
When we are dealing with the thumbnails, those are much smaller files (e.g. Some pre created icons in the apps). This is where SSD significantly better than HDD.
When the apps try to load 100 photos icons for you to preview. The latency required between file loading will x100.
On a traditional HDD. This latency can easily roll up to >10 seconds in total. That's what you usually experience with a HDD. e.g. After fresh boot, the desktop icon slowly appear one by one. Of when browsing through a photo library, the photo slowly appear one by one.
For a SSD, the total latency can be 30-100 times smaller. Which means a 15s latency on a HDD can be reduced to 0.5s or even less. For photos work, you will see almost all photos preview / icons appear within a second (may be you can still see them appear one by one, but with very high speed).
The whole idea of using SSD is to reduce latency, the more small files you deal with, the more you can benefit from SSD. For someone who deal with super large files (e.g. 100GB videos), then a PCIe SSD is preferable, because it can offer super high sequential read / write speed as well. But that usually not required for photos work.
Even though you often copy multi GB files around. A single PCIe SSD wouldn't help. Because when you copy to / from this super fast SSD, the other side will become the bottleneck in a second (e.g. Your HDD). So, you can hardly utilise the top speed. (Copying inside the SDD do able to utilise the speed, however, I don't think it's a normal ops for most people).
50MB RAW may be considerd as a large file in photos. But sure not considered large for SSD. Also, when you dealing with photos. e.g. Loading their metadata, these ops are also only dealing with some small size data. Again, what you are looking for is low latency, which means almost any cheap SSD can do the job well. You can search and compare "4k random read performance" for a particular SSD, that's the pointer of how low latency of that SSD. Then you will realise there is not much difference from the cheapest SATA SSD to the most expensive PCIe AHCI SSD.
I personally will avoid fusion drive. FD will store the data that have high access rate to the SSD part. That also means, when you first time deal with the photos (the 1st time you access it), you may receive zero benefit from FD. That's a bit meaningless for the upgrade (I don't think you are dealing / editing the same photo everyday). Again, if you only want faster boot / apps loading time. SSHD can do the job well.
