pvdisplay

What is pvdisplay?

The pvdisplay command is a powerful tool within the LVM suite. It displays detailed information about your Physical Volumes (PVs). These PVs are the building blocks of LVM; they are partitions (or entire disks) dedicated to being part of an LVM volume group. pvdisplay reveals information about each PV, allowing you to monitor their status, size, and usage.

Basic Usage

The simplest use of pvdisplay is just typing the command itself:

pvdisplay

This will output information about all PVs on your system. The output will include:

• PV Name: The unique identifier for the PV.
• VG Name: The Volume Group the PV belongs to.
• PV Size: The total size of the PV.
• PE Size: The Physical Extent size – the fundamental unit of storage within LVM.
• PE Total: The total number of Physical Extents.
• Free PE: The number of free Physical Extents available within the PV.
• PV Status: Indicates whether the PV is active (allocatable), inactive, or in some other state.

Displaying Information About Specific PVs

You don’t need to view all PVs at once. To display information about a specific PV, provide its device path as an argument:

pvdisplay /dev/sda2

This command will only show details for the PV located at /dev/sda2. Replace /dev/sda2 with the actual path of the PV you’re interested in.

Understanding the Output

Let’s examine a sample pvdisplay output:

  PV Name               VG Name         PV Size   PE Size PE Total Free PE
  /dev/sda2             myvg           10.00 GiB  4.00 MiB   2560    0

This tells us that:

• A Physical Volume (/dev/sda2) exists.
• It belongs to a Volume Group named myvg.
• It’s 10 GiB in size.
• Each Physical Extent is 4 MiB.
• It contains 2560 Physical Extents, and none are free.

Using pvdisplay for Troubleshooting

pvdisplay isn’t just for informational purposes. Its output is helpful when troubleshooting LVM-related issues. For example, if you encounter storage problems, checking the PV Status can quickly reveal whether a PV is offline or inaccessible, pointing you towards the source of the problem. An inactive PV would indicate a potential hardware failure or a configuration problem needing attention.

Advanced Options (Brief Overview)

While the basic usage covers many scenarios, pvdisplay offers additional, albeit less frequently used, options. Consult the man pvdisplay page for a detailed list and detailed explanations. These often involve manipulating the output format or filtering information.

Practical Example: Identifying a Failing PV

Suppose your system is experiencing slowdowns, and you suspect a failing hard drive. Running pvdisplay could pinpoint the problematic PV:

pvdisplay

If you see a PV listed with a status other than allocatable, it might be the culprit. This warrants further investigation, potentially involving hardware diagnostics.