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====== ZFS - Filesystems - Set Properties for a Filesystem ======

Many Properties can be set.

----

===== Compression =====

<code bash>
sudo zfs set compression=on testpool/projects
</code>

<WRAP info>
**NOTE:**  The default Compression is lz4.

  * lz4 is significantly faster than the other options while still performing well; 
  * lz4 is also the safest choice. 

The compression level can be changed if required:

<code bash>
sudo zfs set compression=gzip-9 testpool
</code>

The compression type can be changed too:

<code bash>
sudo zfs set compression=lz4 testpool
</code>

The compression level can be checked:

<code bash>
sudo zfs get compressratio
</code>

</WRAP>

----

===== Copies / Ditto Blocks =====

Ditto blocks create more redundant copies of data to copy, just for more added redundancy.

  * With a storage pool of just one device, ditto blocks are spread across the device, trying to place the blocks at least 1/8 of the disk apart.
  * With multiple devices in a pool, ZFS tries to spread ditto blocks across separate VDEVs.
  * 1 to 3 copies can be can be set.


<code bash>
sudo zfs set copies=3 testpool/projects
</code>

<WRAP info>
**NOTE:**  This sets 3 copies on testpool/projects.
</WRAP>

----

===== Deduplication =====

ZFS dedup will discard blocks that are identical to existing blocks and will instead use a reference to the existing block.

  * This saves space on the device but comes at a large cost to memory.
  * The dedup in-memory table uses ~320 bytes per block.
  * The greater the table is in size, the slower write performance becomes.

<code bash>
sudo zfs set dedup=on testpool/projects
</code>

<WRAP info>
**NOTE:**  There are pros and cons to deduping.

  * Generally, De-duplication is almost never worth the performance penalty. 

</WRAP>

----

===== Mount Point =====

<code bash>
zfs set mountpoint=/test testpool/projects
df -h |grep /test
</code>

----

===== Quota =====

<code bash>
sudo zfs set quota=10G testpool/projects
</code>

<WRAP info>
**NOTE:**  This sets a maximum quota of 10 gigabytes.

  * The Filesystem cannott use more than this amount.

</WRAP>

----

===== Reservations =====

<code bash>
sudo zfs set reservation=200m testpool/tmp
</code>

<WRAP info>
**NOTE:**  This much space is reserved for the Filesystem.

  * It will not be available to other Filesystems.
  * When a Quota is defined first, a reservation cannot be higher than quota.

</WRAP>