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content/2.general/2.storage/2.zfs.md

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+title: ZFS
+main:
+  fluid: false
+---
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+# ZFS
+
+::alert{type="info"}
+🎯 __Objectives:__
+- Understand what ZFS is and why it's useful
+::
+
+ZFS is widely used in the world of servers, NAS systems (like FreeNAS / TrueNAS), virtualization, and even by tech-savvy individuals who want reliable storage. It is both a _file system_ (like NTFS for Windows, EXT4, FAT32, etc.) and a _volume manager_ (similar to LVM).
+
+To put it simply:  
+- A **volume manager** organizes physical storage (like one or more hard drives).  
+- A **file system** organizes how data blocks are written, read, and deleted within those volumes.
+
+ZFS goes far beyond traditional file systems in terms of performance and features.  
+Here’s what we’re most interested in:
+- Its __snapshot management__ features, allowing you to quickly roll back in case of issues.
+- Its support for disk groupings and [__RAID-like structures__](/general/raid) (Z-Mirror, RAIDZ1, RAIDZ2, RAIDZ3).
+- Its __automatic recovery of corrupted data__ (through scrubbing).
+- Its performance, enhanced by RAM caching (ZFS ARC).
+- Its robust error notifications and monitoring.
+
+## Structure
+---
+![](/img/global/zfs.svg)
+
+ZFS has a unique structure:
+
+- **vdev** (virtual device): a group of physical or virtual disks.
+- **zpool**: a collection of vdevs configured as a single storage pool. A zpool can contain multiple vdevs, but a vdev belongs to only one zpool.
+- **dataset**: a logical data container within a zpool. Each dataset can have its own settings (compression, quotas, permissions, etc.).
+
+There are several dataset types:
+- **file system**: a standard ZFS filesystem, mounted without storage quotas.
+- **zvol**: a "virtual disk" with a defined size, which you can format and partition as if it were a physical disk.
+- **snapshot**: a frozen-in-time version of another dataset. Snapshots can be created manually or through backup tools. They can be mounted to browse data as it was at the snapshot time.
+
+## Why ZFS over others?
+---
+### Data Integrity
+
+ZFS continuously checks that your stored data hasn't become corrupted. Every block of data is associated with a checksum, allowing ZFS to detect even the smallest alteration. If corruption is found and a healthy copy exists elsewhere, ZFS can repair the data automatically.
+
+### Built-in RAID
+
+ZFS includes its own volume management system (vdevs). You can build a zpool using multiple disks—similar to traditional [RAID](/general/raid) setups—but with more flexibility. For example:
+- **Z-mirror** → equivalent to RAID 1
+- **RAIDZ1** → equivalent to RAID 5 (tolerates 1 disk failure)
+- **RAIDZ2** → equivalent to RAID 6 (tolerates 2 disk failures)
+- **RAIDZ3** → tolerates up to 3 disk failures
+
+ZFS handles all this natively—no external RAID software needed.
+
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+- Check out the [article on RAID](/general/raid) to find the right solution for your needs.
+:::
+::
+
+### Snapshots and Clones
+
+ZFS allows you to create snapshots—instantaneous images of a dataset's state. Snapshots take up minimal space and can be scheduled frequently. You can also create clones: writable copies of snapshots.
+
+### Compression and Deduplication
+
+ZFS can compress data on the fly (transparently to the user), saving disk space. It also supports deduplication (removing duplicate data), though this feature requires a lot of memory and is not recommended for all use cases.
+
+---
+
+Now you know why ZFS is *the* file system to deploy on your NAS.