I measured Photoshop launch time on the Fusion Drive, a HDD-only partition and on a PM830 connected via USB 3.0.
It ended up being a good benchmark for pseudo-random read performance on Fusion Drive where the workload is too big (or in this case, artificially divided) to fit on the SSD partition alone. In particular, Photoshop CS6 remained partially on the SSD and partially on the HDD. I suspect this is a bug that isn't triggered through normal automated testing (for obvious reasons), but it did create an interesting situation that I could exploit for testing purposes.Īlthough launching any of the iMac's pre-installed applications frequently used by me proved that they were still located on the SSD, this wasn't true for some of the late comers. If I hammered on the Fusion Drive enough, with constant very large sequential writes (up to 260GB for a single file) I could back the drive into a corner where it would no longer migrate data to the SSD without a reboot (woohoo, I sort of broke it!). Unfortunately, I couldn't find a good application use case to generate 4GB+ of pseudo-random data in a repeatable enough fashion to benchmark. The FD/HDD gap would grow for less sequential workloads. In this particular test the gains don't appear all that dramatic, but again that's mostly because we're looking at relatively low queue depth sequential transfers. The breakdown accurately sums up my Fusion Drive experience: nearly half-way between a hard drive and a pure SSD configuration. The results are a bit biased in favor of the HDD-only configuration since the writes are mostly sequential: I timed the process, then compared it to results from a HDD partition on the iMac as well as compared to a Samsung PM830 SSD connected via USB 3.0 to simulate a pure SSD configuration.
Imac fusion drive vs ssd benchmark full#
The resulting files were big enough that by the time I hit photo 297, the 4GB write buffer on the SSD was full and all subsequent exported photos were directed to the HDD instead.
I took my iPhoto library with 703 photos and simply exported all photos as TIFFs. By now my Fusion Drive was over 70% full, which meant the SSD was running as close to capacity as possible (save its 4GB buffer). In trying to come up with a use case that spanned both drives I stumbled upon a relatively simple one. If you do fill the drive up and test with a dataset < 4GB, then you’ll once again just measure SSD performance. If you don’t fill the Fusion Drive up, you can write tons of data to the drive and it’ll all hit the SSD.
Putting Fusion Drive’s Performance in Perspectiveīenchmarking Fusion Drive is a bit of a challenge since it prioritizes the SSD for all incoming writes.