Seven years ago, SanDisk announced its first 1GB flash memory SD card (macworld.com/6218); it had an estimated street price of £205. These days, for the same money, you could buy a 128GB solid-state drive (SSD), based on NAND flash. The drop in price means that it’s become reasonable to consider an SSD as an extra drive for your Mac, or even as a replacement for the built-in hard drive. 

Most mainstream solid-state drives top out at 256GB. (Some vendors have announced 400GB SSDs, but at press time those drives were not yet available.) That’s bigger than the internal drives found in entry-level MacBooks, but smaller than the multiterabyte standard drives currently available. That same £205 could buy you six 250GB 5400rpm drives, or three 500GB drives with a faster 7200rpm rotational speed. 

So why would you want to spend more money for less storage capacity? There are several reasons, including durability, noise and energy consumption. But for most people considering an SSD, the most compelling reason is speed: SSDs can have read and write times that are four to five times faster than a standard spinning hard drive. So, are such improvements worth the additional investment?

Driven to perform
To test the performance benefits of SSDs over standard rotating hard drives, we tried out eight of the devices. They ranged in price from £171 for a 128GB Kingston SSDNow V series drive (www.kingston.com/ukroot/) to £524 for a 256GB WD SiliconEdge Blue drive (www.wdc.com). Price per gigabyte ranged from £1.34 (that 128GB SSDNow V Series Drive) to £2.62 (100GB Mercury Extreme Pro RE SSD [macworld.com/6221]). All are 2.5in internal models.

To test them, we installed each one in turn into a late-2008 unibody MacBook with a 2.4GHz Core 2 Duo processor and 2GB of RAM. Not only was the system ripe for an update, but its hard drive is also easily accessible. 

To establish a baseline, we tested the MacBook’s standard internal drive (a 5400rpm 2.5in Toshiba). We then ran the same tests on a 320GB WD Scorpio Black 7200rpm drive – faster than the standard one, but much less expensive than an SSD.

On average, all but one of the SSDs were between 42 and 48 per cent faster than the MacBook’s stock drive. (The lone outlier – the Kingston SSDNow V series – was only 33 per cent faster; its test results were so erratic that we had to run each test five times or more and then average the results.)

Overall, the OCZ Vertex was the fastest of the SSDs. It scored the best times in four of our five hand-timed tests. It was 75 per cent faster than the stock drive at duplicating a 1GB file, 53 per cent faster when unzipping a 2GB folder in the Finder, and 59 per cent faster when opening a 300MB Photoshop file.

In addition to our real-world stopwatch tests, we also ran the AJA System Test (an automated benchmark that mimics the throughput of video files). Again, the SSDs were a lot faster than the standard spinning models.

For example, in the write tests, the MacBook’s stock hard drive averaged 46MBps. The slowest SSD (the Kingston SSDNow V series) averaged 143MBps – more than three times faster than our spinning hard disk. Four of the SSDs neared 200MBps. 

Reliability concerns
SSDs are new to the consumer desktop, especially on the Mac, and there are questions about how well their reliability and performance will hold up over time. The concern is that the longer you use an SSD, the worse it will work. 

Fortunately, several technologies address that problem; if you are shopping for an SSD, check to see that it supports the following technologies: Wear-levelling manages where data is written, to avoid using the same data cells over and over again. Overprovisioning sets aside some available storage space for administrative purposes and for backing up dead or corrupted data blocks. A third technology – TRIM – allows the operating system to manage garbage collection and reallocation of blocks after data has been deleted. Unfortunately, Mac OS X doesn’t support this last one.

The bottom line
There’s no doubt that SSDs are faster than traditional 2.5in rotating hard disks. But are they fast enough to compensate for their higher prices and lower capacities? Only if you’re really rich or your job needs the fastest performance possible.

If you do decide to go with an SSD, note that the OCZ Vertex was the fastest one we tested. If peace of mind matters to you, consider the OWC Mercury Extreme Pro RE SSD, which is speedy and comes with a five-year warranty. For now, the Kingston SSDNow V Series drive’s erratic performance prevents us from recommending it.