MacBook SSDs Inconsistent, but Negligible

Tests have shown that MacBook Air laptops could perform very differently depending on which model hard drive is installed in the machines. The models in question use Solid State Drives, or SSDs, in place of traditional hard drives.

The SSDs work in a similar way to RAM (random access memory), or flash drives, as they have no moving parts. Although more expensive, SSDs have several key advantages over traditional drives: they make no discernible noise, are less vulnerable to damage from shocks, can access information much more quickly, and are considerably smaller in physical size. They also tend to be much lighter and can be produced in a flatter shape, making them particularly useful for laptops.

New Models Have Different SSD Suppliers

In the most recent updates to the MacBook Air range, Apple's most expensive laptops, both the 11 and 13 inch models have 128GB SSDs. However, the 11 inch model has an SSD produced by Samsung while the 13 inch model has an SSD from Toshiba.

Several tech sites have been testing the performance of the new models and spotted a disparity. The TLD Today podcast found that the 11 inch model can write at 246 MB/s and read at 264 MB/s, while the 13 inch model is limited to 156 MB/s writing and 208 MB/s reading. Overall, that makes the 11 inch model's drive more than 40 per cent faster. (Source: youtube.com)

Meanwhile, tech site Endgadget compared the new 13 inch model with its predecessor, which had a Samsung SSD. In this case, the new model achieved 184 MB/s writing and 203 MB/s reading, whereas the previous model achieved 215 MB/s writing and 203 MB/s, making it around 36 per cent faster. (Source: engadget.com)

How SSDs Compare to Standard, Modern Hard Drives

In comparison, modern 1 or 2 terabyte (TB) hard drive will transfer approximately 40-60 MB per second with an access time of 15ms-25ms (milli-seconds). Newer generation SSDs with a Sandforce controller (SF-1200) will do 285MB/sec sustained with 0.1ms access time.

The access time refers to the time it takes for a hard drive head to locate information on a hard disk platter. Since SSD's have no platter or read/write head (they are essentially made of silicon chips), the access time is only 0.1ms, which makes for an almost instantaneous response when something is loaded or accessed on a PC.

Real World Differences Likely Negligible

With regard to the SSDs being used in the MacBook: in all likelihood, the difference in load and access times would not be discernable to the user.

That's because most of the time the MacBook reads from or writes to the SSD, the amount of data is small enough that at any of the speeds mentioned in the tests it will appear instantaneous. Simply put: the only time it would make a major difference is if there was extremely large files being transferred or loaded into memory all at once. That makes for a reasonable rare scenario.

Another point in Apple's defense is that the company only advertises the storage capacity of the drives in its computers, and makes no specific mention of the read or write speeds.