&quot;You can see the full list of (larger) improvements since the Oracle ZFS&#x2F;OpenZFS split here: <a href="http:&#x2F;&#x2F;open-zfs.org&#x2F;wiki&#x2F;Features&quot;" rel="nofollow">http:&#x2F;&#x2F;open-zfs.org&#x2F;wiki&#x2F;Features&quot;</a><p>I searched that page (and this HN discussion) for the word &quot;defrag&quot; and got nothing.  That&#x27;s a problem.<p>Does the Oracle version of ZFS have defrag, or have it in the pipeline ?<p>It is <i>not</i> reasonable to expect folks to just never, ever, exceed 85% pool utilization.  Further, most of those folks don&#x27;t realize that there&#x27;s no coming back from it - exceed 85% even for a day and you have a performance penalty <i>forever</i>.<p>&quot;Oh it&#x27;s no problem, just export the pool and recreate it&quot;<p>Sure ... let&#x27;s buy another $20k of equipment and duplicate a 250 TB pool just because we had a usage overrun (which wasn&#x27;t really a usage overrun at all) one weekend.<p>Finally:  think of the economics of this unofficial limit on your pools ... you probably aren&#x27;t running a pure stripe, right ?  Maybe you&#x27;re running raidz3 ?  So you already gave up three drives for data protection ... did your cost accounting also subtract <i>another</i> 15-20% from available storage space ?<p><i>ZFS needs defrag</i>.