(The whole point of this is a question about hard drive adapters, but I’ve never learned to make a long story short. Hang in there, please!)

My IBM 320 SSDs reached their five-year warranty date without a hitch last month. I had two of them in an IcyDock housing in a RAID 0 configuration running 10.6.8. I paid £260 for the two 80 Gb drives in 2011. Why wait for them to fail? I figured I’d replace them with a 240 Gb Toshiba Q300 SSD for £50.

I needed an adapter to fit the 2 1/2” drive onto the sled in my 2010 Mac Pro. I ordered a £11 “General 2.5" SSD to 3.5" SATA Hard Disk Drive HDD Adapter Caddy Tray Cage Hot Swap Plug” from Amazon. A few days later I found out it was coming from China and the delivery date was supposed to be May 4. I already had my Toshiba SSD and wanted the adapter NOW! So, I bit the bullet and ordered an “ICY DOCK EZConvert Air Lite MB482SP-3B SATA I, II, & III 2.5" to 3.5" Hard Drive/Solid State Drive Converter/Mount” from SCAN in the UK. The original Amazon order surprised me by arriving the next day.

So, I screwed the SSD to the adapter, plugged it in and divided it into equal 120 Gb partitions – one for 10.6.8, one for 10.11.4.

I have a free utility called XBench. I don’t know how accurate it is, but it’s sort of like my bathroom scales: as long as it sets a baseline, the main thing is, is the score better or worse.

I ran XBench on a 7,200 rpm spinner. The result was 80. I ran XBench on my main drive: a 120 Gb Samsung EVO SSD mounted on a PCIe card. The result was 767. I ran XBench on the Toshiba mounted on the sled in the normal hard drive bay. The result was a disappointing 314.

Today, the SCAN delivery arrived. I took the £11 adapter out and replaced the Toshiba Q300 in the new £16 adapter. The XBench result was 430.

Does this seem right? That an adapter that is basically just a simple double-ended plug should yield such a different result?

Mainly, I was impressed with how much faster the SSD on the PCIe card is.

I can't speak to your specific adapter, but elsewhere people have commented on the "Made in China" USB cables, Lightening and Thunderbolt cables. They have observed quality differences.

Three things are going to have the most effect on your benchmarking: the drive, the bridge chip, and the computer interface.

Firewire is usually pretty easy to quantify, either 400 or 800 mbit. USB can vary greatly depending on the computer and the type, USB1 is 12, 2 is u to 480, usb3 5gbit, 100t ethernet is 100 and gig is 1gbit. I divide those numbers by 9 for a fair speed estimate. Older computers do quite poorly on USB due to processor overhead, sometimes cutting speed down by 30-50%. (PPC macs running USB2 generally never get faster than 26MB/sec) Thunderbolt is usually faster than whatever drive you are using, until you get into fast SSDs on both ends.

The bridge chip in use can have a dramatic effect on transfer speed, especially on USB, which USB2 typically clocks very close to FW400, at 39MB/sec. The most common speeds I've seen USB2 run at are 18, 26, or 36MB/sec, and a few as slow as 8 or 12. The good new ones run closer to 38-39.

So there's a lot of chance for variation, and your adapter can make a huge difference. Most hard drives will move at least 79MB/sec, 130-ish is more common. SSD-to-SSD copies can be frighteningly fast. I have a lacie SSD on thunderbolt that copies gigabyte size files to my retina in Finder so fast that the progress window never appears. Makes my gigabit ethernet connection looks low.

Also keep in mind that some reviewers are NOT good judges of speed, since they may be comparing against crap for hardware. You really need to overlook "fast!" and look for hard numbers. I have one of those adapters with several ends on it in the bag - it's not too fast but it's handy. I have a faster one I keep at my desk that has a less transportable power adapter.