Tuning Techniques for Writes

Fusion-io is the only company that enables you to format solid state storage for optimal write performance. This section discusses performance tuning techniques, as well as considerations for writes.

Increased Steady-State Write Performance with fio-format

Under sustained, random writes, which are written randomly across the entire ioDrive, write performance will decrease. This decreased write performance is referred to as steady-state write performance.

There are very few real-world storage use cases that create this sort of write workload, the most common being RDBMS systems. However, the most common activity that triggers this behavior is running micro benchmarks rather than real-world applications.

Unlike drive form factor devices, the ioDrive can be tuned to achieve a higher steady-state write performance than what it is shipped with from the factory. The first line of tuning is to provide the ioDrive with additional working capacity, or reserve (storage capacity that is not visible but is usable by the ioDrive for internal optimization). Changing this reserve capacity can be done using the fio-format utility. Running fio-format changes the reserve size and affects the overall long term performance of the ioDrive. Repeated fio-formats are not required to get proper performance, unless the initial change in reserve size did not yield the needed steady-state write performance.

A recommended starting point is decreasing the drive's capacity by 25%. For example, if the drive is a 160 GB drive, you would fio-format it to 120GB

Warning: This will destroy all data on the drive!

Assuming the drive that you would like to format is /dev/fct0 (use fio-status to determine this), you would use the following commands:

$ fio-detach /dev/fct0

$ fio-format -s 120G /dev/fct0

$ fio-attach /dev/fct0

The following graph shows the effect of reserve on write performance under some circumstances. This graph shows that the larger the reserve, the better the steady-state performance achieved.

Figure 17 – Effect of increased reserve space on write performance