System Monitor can monitor the current performance values for disks currently connected to your computer. The current sums of the read and written data of all disks selected are displayed in the menu bar in this case. The term disks should denote all objects which identify themselves to the computer as being block-oriented storage devices. Next to hard drives, this includes optical disks, floppy drives, or storage card readers, for example.
If you like to monitor disks of your computer, perform the following steps:
Only those disks will become part of the statistics which you have selected for monitoring (see below).
The data shown is calculated live and updated about once per second.
The box Menu Bar controls in which form disk performance should be displayed. System Monitor offers a variety of icons and functions that you can combine in any order. The following elements can be used:
Within the box, the upper bar simulates as a sample how this monitor section should be presented in the menu bar. You can grab the individual items by mouse and move them into a different order. You can remove an element by pulling it out of the bar. The lower bar contains the stock of items available. If you like to add a certain item to the menu bar, use the mouse to drag it from the lower to the upper bar. Pressing the button Default causes your current settings to be deleted, replacing it by a default suggestion for the menu bar.
If you mistakenly have removed all items of this monitoring section from the menu bar, a three-star-icon (⁂, asterism) will appear as a placeholder. This ensures that you still can open the associated menu.
You cannot drag items directly into the real menu bar because Mac OS X does not allow this.
At least the following items will be shown for each selected disk as part of the menu associated with this monitor section:
The history graph in the menu bar and the individual history graphs in the menu can be shown in different modes of operation. The following options can be set:
Display Style: If you select Back and Front, the read data rate will be displayed dark at the back, the write data rate will be displayed lighter in front. If you switch to Opposed, the read data rate will be displayed in the lower half of the graphics, growing from bottom upwards, the write data rate will be displayed in the upper half of the graphics upside down, growing from top downwards.
Automatic Zoom: The history will automatically focus on the value range observed in the presented 30 seconds. The curve will always be magnified to make the graph cover a certain area. In the mode Scale to peak since start, the curve will be magnified to a degree that the maximum of the curve will match the maximum of values System Monitor has observed so far. This is the “most honest” mode of operation: If the monitored values have found their level after some time, the peak in the graph will match the peak performance the monitored disk can provide. Small data transfer rates, however, can become invisible because they might be so small compared to the peak value that they can no longer be represented graphically. The alternative is the setting Magnify displayed interval. Here, the zoom factor will be tuned each second, attempting to always make the smallest details found in the last 30 seconds visible. However, the magnification can now switch back and forth unpredictably, with small changes leading to an exaggerated impression. Both settings have their advantages and disadvantages.
The table Include the following disks allows you to control which drives should be monitored by the app and which shouldn't. Set a check mark next to each disk which should be monitored and remove the check marks for disks where no monitoring should be performed. The selection can also be applied to all entries automatically, using the buttons All or None. The lines in the table can be dragged to a different sort order if desired. This order will then be used for the corresponding sections in the menu.
Monitoring of metrics in this section is optimized for permanently connected devices. If you switch off or add drives, there will be no guarantee that all changes will immediately become visible in the selection table and in the menu.