From the article:-
Specifically, it has been found that the $1,299 base model with 256GB of storage is significantly slower SSD read and write speeds compared to the equivalent previous-generation 13-inch MacBook Pro. YouTube channels such as Max Tech and Created Tech tested the 256GB model with Blackmagic’s Disk Speed Test app and found that the SSD’s read and write speeds are around 1,450 MB/s, which is approximately 50 percent slower read and 30 percent slower write compared to the 13-inch MacBook Pro with the M1 chip and 256GB of storage .
Disk Speed Test app numbers shared by Max Yuryev of Max Tech:
13-inch MacBook Pro (M1/256GB) Read Speed: 2,900
13-inch MacBook Pro (M2/256GB) Read Speed: 1,446
13-inch MacBook Pro (M1/256GB) Write Speed: 2,215
13-inch MacBook Pro (M2/256GB) Write Speed: 1,463
Yuryev disassembled the new 13-inch MacBook Pro and discovered that the 256GB model features only a single NAND flash storage chip internally, whereas the previous model has two NAND chips that are likely 128GB each. This difference probably explains why the new model has a slower SSD, as multiple NAND chips allow for faster data transfer speeds in parallel.
Slower SSD performance appears to be limited to the 256GB version of the 13-inch MacBook Pro, as higher capacity machines have not demonstrated the same issue. As noted on the MacRumors forums, Aaron Zollo ran the Disk Speed Test app on the 512GB model and the SSD’s read and write speeds were similar to all M1 models. This means that the 512GB model likely remains equipped with two 256GB flash storage chips.
The base model’s slower SSD speeds were not mentioned in embargoed reviews of the notebook, as it appears that Apple provided many reviews with a 1TB configuration for testing.
Yuryev has also suggested that the 256GB SSD in the 13-inch MacBook Pro underperforms in day-to-day use due to its use of the storage as virtual memory when the 8GB unified memory is maxed-out. The virtual memory swapping results in slower system performance overall, but it is more pronounced on devices with slower SSDs.
For example, the M2 MacBook Pro with 256GB SSD and 8GB RAM was slower than the M1 MacBook Pro with 256GB SSD and 8GB RAM across multiple usage tests involving Photoshop, Lightroom, Final Cut Pro, multitasking, and file transfers. In a multitasking RAM test, the M1 consistently loads content faster with multiple apps open, and in a 50 image export test in Lightroom with apps open, the M1 was again quicker. It was able to export 50 images in 3 minutes and 36 seconds, while the M2 took 4 minutes and 12 seconds. These results were across all of the performance stress tests and benchmarks undertaken by Max Tech.
It’s unclear why the new base model 13-inch MacBook Pro is only equipped with a single NAND chip, but costs and/or supply constraints are two possible factors. Customers will need to spend at least $1,499 on additional storage to avoid the smaller, slower storage pool that comes with the 256GB base model. It remains to be seen if the new MacBook Air with the M2 chip will also have slower SSD speeds when configured with 256GB of storage.”