What is ZFS snapshot?
What is ZFS snapshot?
A snapshot is a read-only copy of a file system or volume. Snapshots can be created almost instantly, and they initially consume no additional disk space within the pool. Snapshots use no separate backing store. …
Is a ZFS snapshot a backup?
You can send data incrementally with pretty much any backup solution, but with ZFS any snapshot can be used as the first version of the data to send to another location. Once the first snapshot is fully sent to another location then you can choose to send all subsequent snapshots or skip snapshots.
How do I enable ZFS snapshots?
You can enable or disable these services from the command line or from the System->Preferences->Time Slider Setup menu. From this menu, you can also customize which ZFS file systems to snapshot and adjust the file system capacity setting for when snapshots are removed.
How do I restore a ZFS snapshot?
Restoring Data with ZFS Snapshots
- Create a filesystem:
- Create a snapshot with no data inside the filesystem:
- List out the filesystems and snapshots (otherwise known as children) for the yesYouCan filesystem:
- Start adding data into the filesystem’s mountpoint.
- Run the list command again.
Where are ZFS snapshots stored?
Snapshots of file systems are accessible in the . zfs/snapshot directory within the root of the file system. For example, if tank/home/ahrens is mounted on /home/ahrens , then the tank/home/ahrens@thursday snapshot data is accessible in the /home/ahrens/. zfs/snapshot/thursday directory.
How big is a ZFS snapshot?
The actual meta-data of snapshots are negligible. As a copy-on-write file system, ZFS snapshots only require space for modified data; creating a snapshot does not immediately duplicate everything. If you have a snapshot of given size, and then add or modify files summing up to 100GB, the snapshot will “cost” you 100GB.
How do I use ZFS Clone?
To create a clone, use the zfs clone command, specifying the snapshot from which to create the clone, and the name of the new file system or volume. The new file system or volume can be located anywhere in the ZFS hierarchy.
What is ZFS promote?
You can use the zfs promote command to replace an active ZFS file system with a clone of that file system. This feature enables you to clone and replace file systems so that the original file system becomes the clone of the specified file system.
Is ZFS the best file system?
Sad as it makes me, as of 2017, ZFS is the best filesystem for long-term, large-scale data storage. Although it can be a pain to use (except in FreeBSD, Solaris, and purpose-built appliances), the robust and proven ZFS filesystem is the only trustworthy place for data outside enterprise storage systems.
Where do I Find my snapshots in ZFS?
By default, snapshots are no longer displayed in the zfs list output. You must use the zfs list -t snapshot command to display snapshot information. Or, enable the listsnapshots pool property. For example: Snapshots of file systems are accessible in the .zfs/snapshot directory within the root of the file system.
What do snapshots and clones do in ZFS?
In this tutorial we will learn about ZFS snapshots and ZFS clones, what they are and how to use them. A snapshot is a read-only copy of a filesystem taken at a moment in time. Snapshots only record differences between the snapshot and the current filesystem.
How does the space consumed by ZFS work?
As the file system changes, space that was previously shared becomes unique to the snapshot, and thus is counted in the snapshot’s used property. Additionally, deleting snapshots can increase the amount of space that is unique for use by other snapshots.
How does the user reference count change in ZFS?
Each snapshot has an associated user-reference count, which is initialized to zero. This count increases by 1 whenever a hold is put on a snapshot and decreases by 1 whenever a hold is released.