My Oracle Support Banner

Understanding How ZFS Calculates Used Space (Doc ID 1369456.1)

Last updated on APRIL 10, 2024

Applies to:

Solaris Operating System - Version 10 6/06 U2 and later
Oracle ZFS Storage Software
Information in this document applies to any platform.


This document explains how ZFS calculates the amount of used space within a zpool and provides examples of how various ZFS features affect that calculation.


To view full details, sign in with your My Oracle Support account.

Don't have a My Oracle Support account? Click to get started!

In this Document
 Example #1: Creating snapshots and calculating space used.
 Example #2: Using Quotas
 Example #3: Setting Reservations
 Example #4: ZFS Volumes (ZVOL)
 Example #5: Overlaid Mounts
 Example #6: Using zdb(1M) and mdb(1M) to look for large files and directories or files in the ZFS Delete Queue
 Example #7 - LUN Expanded without expanding the zpool
 Frequently Asked Questions - FAQ
 Why don't du and df report correct values for ZFS space usage?
 Why doesn't ZFS space used as reported by zpool list and zfs list match?
 Why creating a snapshot immediately reduces the available pool size
 Example #8 - ZFS Appliance BUI Issues

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.