ZFS Virtual Devices Test

Each storage pool is comprised of one or more virtual devices. A virtual device is an internal representation of the storage pool that describes the layout of physical storage and its fault characteristics. As such, a virtual device represents the disk devices or files that are used to create the storage pool.

Slow, overloaded virtual devices can delay accesses to the ZFS, thereby causing the user experience with the file system to suffer. This test enables administrators to isolate slow devices and understand how I/O load is distributed across devices, so that administrators are forewarned of slowdowns and/or abnormal load conditions.

Target of the test : A Solaris host

Agent deploying the test : An internal agent

Outputs of the test : One set of results for each virtual device in a storage pool

Configurable parameters for the test
  1. Test period - How often should the test be executed
  2. Host - The host for which the test is to be configured.
  3. port - Refers to the port used by the specified host. Here it is NULL.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Free space:

Indicates the amount of data currently stored in this.

MB

This amount differs from the amount of disk space available to actual file systems by a small margin due to internal implementation details.

Allocated space:

Indicates the amount of disk space available in this device.

MB

This amount differs from the amount of disk space available to datasets by a small margin.

Operations read:

Indicates the rate at which read I/O operations were sent to this device, including metadata requests.

Reads/Sec

High values of these measures are indicative of high levels of I/O activity on a device. Compare the values of these measures across virtual devices to identify the I/O-intensive devices.

Operations write:

Indicates the rate at which write I/O operations were sent to this device.

Writes/Sec

Read bandwidth:

Indicates the bandwidth of all read operations (including metadata) to this device.

Reads/Sec

High values for these measures indicate high bandwidth usage by a virtual device. By comparing the values of these measures across devices, you can isolate those devices that consume bandwidth excessively, and also understand when they consume too much bandwidth - when reading? or writing?

Write bandwidth:

Indicates the bandwidth of all write operations to this device.

Writes/Sec