Defining artificial operating system sensors

In addition to "real" sensors Apple has built into your Mac, Hardware Monitor can also monitor other operational values of your computer. This is done by creating artificial software sensors, which are called Probes. This feature is available in Hardware Monitor only.

You can define an unlimited number of probes that monitor the following aspects of the operating system:

• the current load on each processor core. Load is defined as percentage of time where the processor is actually "doing" anything, as opposed to the time where it is idle.
• the current average load of all processor cores. If your computer contains multiple processing units, the load characterstics will be combined into one single value.
• the current number of processes handled by the operating system.
• disk usage on each volume. Usage is defined as percentage of allocated storage space in relation to total storage space.
• free storage space on each volume, measured in bytes.
• used storage space on each volume, measured in bytes.
• free memory, measured in bytes of physical RAM.
• used active memory, measured in bytes of physical RAM. This is memory in use by running applications and the operating system, which has been accessed in the last few milliseconds.
• used inactive memory, measured in bytes of physical RAM. This is memory in use by running applications and the operating system, which has not been accessed in the last few milliseconds. Although this memory is allocated and in use, these blocks are candidates to be moved out to swap files on the hard disk, in case other applications are needing physical RAM at a more active rate.
• used non-pageable memory, measured in bytes of physical RAM. This is memory in use by running applications and the operating system which is not allowed to be moved out to swap files on the hard disk.
• number of page-ins. This is the number of 4 KB blocks currently being moved from the hard disk into physical memory. This includes swap operations (blocks that were moved out to swap files and are now loaded back), but also includes normal load operations, when applications use optimized access techniques for reading files.
• number of page-outs. This is the number of 4 KB blocks currently being moved from physical memory to the hard disk. This includes swap operations (blocks that are being moved out to swap files), but also includes normal save operations, when applications use optimized access techniques for writing files.
• allocated swap space, measured in bytes of storage space. This is the actual number of bytes currently pre-allocated on the hard drive for use during swap operations. Note that this is not equal to the amount of virtual memory currently swapped out.
• network interface outgoing packets: The number of data packets currently being transferred from the computer to the network on a selected network interface. Hardware Monitor handles this as a unitless counter, but because the interfaces are monitored at a rate of one sample per second, the reading will be equivalent to the transfer speed, measured in packets per second.
• network interface incoming packets: as before, but for incoming data packets.
• network interface outgoing bytes: The number of bytes (displayed as kilobytes) currently being transferred from the computer to the network on a selected network interface. Hardware Monitor handles this as memory size, but because the interfaces are monitored at a rate of one sample per second, the reading will be equivalent to the transfer speed, measured in kilobytes per second.
• network interface outgoing bytes (total): The number of bytes in total (displayed as megabytes) which have been transferred from the computer to the network on a selected network interface since the operating system has been started.
• network interface incoming bytes: analog to the number of outgoing bytes, this probe monitors the incoming bytes.
• network interface incoming bytes (total): analog to the number of outgoing bytes (total), this probe monitors the total number of incoming bytes.
• network interface output errors: the current number of network errors when the selected interface is trying to send data to the network. Hardware Monitor handles this as a unitless counter, but because the interfaces are monitored at a rate of one sample per second, the reading will be equivalent to the number of errors per second.
• network interface input errors: the current number of network errors when the selected interface is receiving data from the network. Hardware Monitor handles this as a unitless counter, but because the interfaces are monitored at a rate of one sample per second, the reading will be equivalent to the number of errors per second.
• network interface collisions: the current number of network collisions seen by the selected interface. Hardware Monitor handles this as a unitless counter, but because the interfaces are monitored at a rate of one sample per second, the reading will be equivalent to the number of collisions per second. Note that only certain network technologies can experience data collisions, for example 10Base-5 shared Ethernet.
• S.M.A.R.T. drive verification status, for each connected drive which is online and supports self monitoring via the S.M.A.R.T. industry standard. The value will be 1 if the drive's diagnostic processor estimates that the drive will survive the near future without failure. The value will be 0 if the drive is estimating that its lifetime is about to end. See also the section Displaying disk monitoring data for more information on S.M.A.R.T. technology.
• RAID operation status, for each software RAID set created by Mac OS X. The value will be 1 if the RAID set is OK and fully operational. The value will be 0 if the status of the RAID set is degraded, e.g. if one disk of the RAID set has failed. Only RAID sets based on Mac OS X system software are supported. You cannot create probes for third-party RAID solutions because there is no common standard to support this.
• electrical power, for each pair of physical voltage and current sensors you define. If your computer contains a voltage and an amperage sensor which both monitor the same object, e.g. a battery unit, or a processor card, you can define a virtual power sensor which automatically computes the electrical power of this object. Note: You are responsible for selecting a pair of sensors for which the definition of power makes sense. Hardware Monitor will allow that you combine electrical sensors which monitor different devices, e.g. the voltage sensor of a battery combined with the amperage sensor of a CPU card, but the resulting power value won't make any sense in this case.
• remaining battery capacity, defined as percentage of current battery capacity in relation to total battery capacity. This is a virtual sensor you can define for each battery unit.

Note: If you are using internal "hot-swap" drives, or external eSATA drives, a probe of the type S.M.A.R.T. drive verification status will also register a hard disk error when you are switching off or removing the drive.

Note: Network interface probes require Mac OS X 10.4 or a later version.

Creating a new probe is possible with the section Probes in the Preferences window of Hardware Monitor. Select the desired type of probe, then press the button + below the left bottom corner of the probe table. If it is necessary, Hardware Monitor will ask for additional data to create the probe, e.g. the processor number for a CPU load sensor, or the hard drive for a virtual S.M.A.R.T. sensor. The probe will be added immediately.

Probes behave the same way as "real" sensors. You can use them without any restrictions, for example to define alerts, to record history data, to display them in output windows, etc.

To delete a probe, select its entry in the table, then press the - button below. History data of a deleted probe will be deleted as well. It is not possible to recover history data of a deleted probe even if you attempt to recreate the same probe later.

It is not possible to create two identical probes, i.e. probes of the same type which monitor the very same object.
Hardware Monitor can create probes for the local computer only. It is possible to monitor probes on remote computers as well, but in this case you'll have to create them with a copy of Hardware Monitor running on the remote computer first.

Table of contents