Demystifying OpenZFS 2.0
EDIT: There is a now an incorrect response to this post of mine stating that I forgot to mention the ZIL SLOG -- but the poster doesn&#x27;t understand how the ZIL SLOG actually works unfortunately. :(<p>I applaud OpenZFS for these major improvements, but its performance is not competitive with some of the commercial offerings, even if OpenZFS is a more easily administered solution.<p>The main issue with OpenZFS performance is its write speed.<p>While OpenZFS has excellent read caching via ARC and L2ARC, it doesn&#x27;t enable NVMe write caching nor does it allow for automatic tiered storage pools (which can have NVMe paired with HDDs.)<p>This means that large writes, those which exceed the available RAM, will drop down to the HDD write speed quite quickly instead of achieving wire speed.  Which means I get write speeds of 300 MBps versus 10 GBps wirespeed.<p>The solutions competitors have implemented are:<p>- SSD read-write caching, usually using mirrored NVMe drives to ensure redundancy.<p>- SSD tiering, which is including your SSDs in your storage pool.  Frequently accessed data is moved onto the SSDs while infrequently accessed data is moved to the HDDs.<p>Without these features, my QNAP (configured with SSD tiering) kicks the pants off of ZFS on writes that do not fit into memory.<p>References:<p>[1] QNAP Tiering: <a href="https:&#x2F;&#x2F;www.qnap.com&#x2F;solution&#x2F;qtier&#x2F;en-us&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.qnap.com&#x2F;solution&#x2F;qtier&#x2F;en-us&#x2F;</a><p>[2] QNAP SSD Read-Write Caching: <a href="https:&#x2F;&#x2F;www.qnap.com&#x2F;solution&#x2F;ssd-cache&#x2F;en&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.qnap.com&#x2F;solution&#x2F;ssd-cache&#x2F;en&#x2F;</a><p>[3] Synology SSD Read-Write Caching: <a href="https:&#x2F;&#x2F;kb.synology.com&#x2F;en-my&#x2F;DSM&#x2F;help&#x2F;DSM&#x2F;StorageManager&#x2F;genericssdcache?version=6" rel="nofollow">https:&#x2F;&#x2F;kb.synology.com&#x2F;en-my&#x2F;DSM&#x2F;help&#x2F;DSM&#x2F;StorageManager&#x2F;ge...</a>