General Topics






Tips and How-To



The recondition command helps restore solid state drive performance by rewriting free space on the drive in very large chunks.

Most solid state drives respond to this treatment by cleaning up and defragmenting themselves. Some top-quality enterprise grade drives do not need reconditioning, such as the OWC Mercury Extreme.

DiskTester can operate on any volume, including the boot volume, but the more free space on the drive, the more efficient the process, so get rid of extra junk before reconditioning.

See Running DiskTester recondition , below. Before testing:

Graphing the results

Graph the results using the supplied spreadsheet.

Iteration summary

DiskTester emits a summary of each iteration when done, even if you stop it before all iterations are done. With iterations equivalent to 3-8 times the full capacity of the SSD (eg 384GB to 1GB for a 128GB SSD), this can provide useful insight as to the effectiveness of the reconditioning process.

This graph shows the behavior (or not) with each iteration. Remember, if there is minimal free space, more iterations are required. Generally speaking total writes of 4-6X the drive capacity are needed; the amount of free contiguous space determines how many iterations are needed.

In the graph below, the green line shows a 53% improvement in average write speed from the first iteration to the 8th one, as well as a 73% improvement in minimum write speed. There is some further improvement to the 9th iteration, then it oscillates around 100MB/sec. The maximum speed of around 170MB/sec has remained stable, and minimum speed has gained as well, so overall performance is much higher after reconditioning.

Click to view larger size

Single iteration

Shown below is a graph for the write speed of a popular brand 128GB SSD for which marketing materials claim a write speed of 190MB/sec, but averages only 60MB/sec! It has seen only light use. And that’s for the best case scenario of huge transfer sizes. This write performance is well below that of a even a slow hard drive, as well as being extremely variable.

Consider graphing the first iteration and the last one, then compare the two.

First iteration over poor-performing 128GB SSD
First iteration over 128GB SSD

Shown below is the 4th iteration. Consistency is better, and write speed is up to 80.3MB/sec, still disappointing, but a 34% improvement over the first iteration.

4th iteration over 128GB SSD

The 8th iteration picks up more speed, averaging about 93MB/sec. This brand SSD doesn’t take a hint all that well, but at least it’s steadily improving.

8th iteration over 128GB SSD

There is some improvement with more iterations, but not a lot. The drive has stabilized around 100MB/sec writes, a bit more than half its claimed write speed. That is why you want an SSD that offers long-term high performance, like the OWC Mercury Extreme.

8th iteration over 128GB SSD

Running DiskTester recondition

Using, choose Recondition SSD.

Reconditioning is a “good enough” process. You can stop it anytime you like, restart it later, etc. Observe the average speed, and when acceptable, stop the process.

DiskTester also monitors the results, and will stop when the average speed does not improve significantly.

Because of the nature of SSDs, results with partially full drives can go fast/slow/fast/etc until the entire capacity has been covered. The drive isn’t really getting faster or slower per se, it’s that different portions of it are being accessed. It’s a little confusing!

DiskTester recondition

Command line usage

Simple. There are no options, only the drive name to recondition.


Specify the volume to be reconditioned. Reconditioning a hard drive is pointless.

disktester recondition XBoot

Next page: fill-volume