hIOmon SSD Performance Monitor - Understanding desktop usage patterns.

[overthere]

Regarding several of the "maximum" I/O operation performance metrics collected by the hIOmon software, here are a couple of "nuances" that folks might want to consider.

The "maximum" IOPS metric reflects the actual number of I/O operations (e.g., read I/O operations obviously in the case of the "max read IOPS" metric) observed by the hIOmon software during a one-second interval since the start of the time duration when the hIOmon software began collecting I/O operation performance data for the respective file, device, or process.

For example, if the hIOmon software saw 5000 read I/O operations performed during a one-second interval (and this was the maximum number of read I/O operations observed so far within a one-second interval), then the reported value would be 5000.

As One_Hertz suggested above, it could be that all 5000 of these read I/O operations were performed during the "first" half-second of the one-second interval. One could subsequently argue that the "potential" maximum rate is really 10000 (since if the device did 5000 in 1/2 second, then it "should" be able to do 10000 within a full second).

In any case, the reported maximum IOPS values reflect that which was actually observed by the hIOmon software based upon actual device usage - and not necessarily the maximum that the device (for example) can perform.

Likewise, the maximum MB/s metric (i.e., the maximum amount of data transferred during a one-second interval) and the "maximum MB/s for a single I/O operation" metric are both based upon actual observations of the hIOmon software during the course of monitored file/device usage. [EDIT] A short description of each of these throughput metrics (and an important distinction between them) can be found at this prior post:

http://www.xtremesystems.org/forums/...3&postcount=64

One other quick note. The maximum metrics described above can sometimes appear to exceed the capability of the device.

Take, as an example, a read I/O operation whose data transfer can be entirely satisfied by the OS without requiring a data transfer directly with the device. In this case, the data transfer is basically a memory transfer operation performed "internally" by the OS without interaction with the device (and so consequently not subject, for instance, to the bandwidth limitations of the actual device interface).

And as a result, the performance characteristics of the read I/O operation (as observed by the hIOmon software based upon the starting time and completion time of the I/O operation along with the amount of data transferred) can appear "exaggerated" in light of the performance expectations/limitations of the corresponding device.