<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>raattgift</author><text>&amp;gt; How is L2ARC not &amp;quot;true hybrid&amp;quot;?&lt;p&gt;It doesn&amp;#x27;t persist across import&amp;#x2F;export or reboot.&lt;p&gt;It is demand-filled.&lt;p&gt;Not all data in the main vdevs are eligible for l2arc.&lt;p&gt;There is memory overhead for l2arc buffers.&lt;p&gt;There is CPU overhead in processing l2arc headers.&lt;p&gt;Once a buffer is in l2arc it stays in l2arc until the underlying data is overwritten or destroyed, or until the l2arc has filled up and the buffer is replaced with fresher data.&lt;p&gt;A true hybrid in the zfs context would let one pin a dataset or zvol onto a particular vdev, or pin only the (zfs) metadata (or a subset thereof) of a dataset, zvol or pool to a particular vdev.&lt;p&gt;Openzfs will eventually get both persistence and this form of true hybrid.&lt;p&gt;Unfortunately automatic migration by zfs of hot data to low-latency vdevs and cool data from low-latency vdevs is not really possible without solving the infamous block-pointer-rewrite problem.</text><parent_chain><item><author>floatboth</author><text>&amp;gt; ZFS never really adapted to today’s world of widely-available flash storage: Although flash can be used to support the ZIL and L2ARC caches, these are of dubious value in a system with sufficient RAM, and ZFS has no true hybrid storage capability.&lt;p&gt;How is L2ARC not &amp;quot;true hybrid&amp;quot;?&lt;p&gt;&amp;gt; And no one is talking about NVMe even though it’s everywhere in performance PC’s.&lt;p&gt;Why should a filesystem care about NVMe? It&amp;#x27;s a different layer. ZFS generally doesn&amp;#x27;t care if it&amp;#x27;s IDE, SATA, NVMe or a microSD card.&lt;p&gt;&amp;gt; can be a pain to use (except in FreeBSD, Solaris, and purpose-built appliances)&lt;p&gt;I think it&amp;#x27;s just a package install away on many Linux distros? Also installable on macOS — I had a ZFS USB disk I shared between Mac and FreeBSD.&lt;p&gt;Also it&amp;#x27;s interesting that these two sentences appear in the same article:&lt;p&gt;&amp;gt; best level of data protection in a small office&amp;#x2F;home office (SOHO) environment.&lt;p&gt;&amp;gt; It’s laughable that the ZFS documentation obsesses over a few GB of SLC flash when multi-TB 3D NAND drives are on the market&lt;p&gt;Who has enough money to get a mutli-TB SSD for SOHO?!</text></item></parent_chain></comment><story><title>ZFS Is the Best Filesystem For Now</title><url>http://blog.fosketts.net/2017/07/10/zfs-best-filesystem-now/</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>chongli</author><text>&lt;i&gt;Why should a filesystem care about NVMe?&lt;/i&gt;&lt;p&gt;Because at some point the filesystem becomes a bottleneck. ZFS was designed with the assumption that CPUs would be way faster than storage. When you get speeds over 10GB&amp;#x2F;sec, [0] you are going to spend a lot of time checksumming all that data.&lt;p&gt;[0] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;www.seagate.com&amp;#x2F;ca&amp;#x2F;en&amp;#x2F;about-seagate&amp;#x2F;news&amp;#x2F;seagate-demonstrates-fastest-ever-ssd-flash-drive-pr&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.seagate.com&amp;#x2F;ca&amp;#x2F;en&amp;#x2F;about-seagate&amp;#x2F;news&amp;#x2F;seagate-demo...&lt;/a&gt;</text><parent_chain><item><author>floatboth</author><text>&amp;gt; ZFS never really adapted to today’s world of widely-available flash storage: Although flash can be used to support the ZIL and L2ARC caches, these are of dubious value in a system with sufficient RAM, and ZFS has no true hybrid storage capability.&lt;p&gt;How is L2ARC not &amp;quot;true hybrid&amp;quot;?&lt;p&gt;&amp;gt; And no one is talking about NVMe even though it’s everywhere in performance PC’s.&lt;p&gt;Why should a filesystem care about NVMe? It&amp;#x27;s a different layer. ZFS generally doesn&amp;#x27;t care if it&amp;#x27;s IDE, SATA, NVMe or a microSD card.&lt;p&gt;&amp;gt; can be a pain to use (except in FreeBSD, Solaris, and purpose-built appliances)&lt;p&gt;I think it&amp;#x27;s just a package install away on many Linux distros? Also installable on macOS — I had a ZFS USB disk I shared between Mac and FreeBSD.&lt;p&gt;Also it&amp;#x27;s interesting that these two sentences appear in the same article:&lt;p&gt;&amp;gt; best level of data protection in a small office&amp;#x2F;home office (SOHO) environment.&lt;p&gt;&amp;gt; It’s laughable that the ZFS documentation obsesses over a few GB of SLC flash when multi-TB 3D NAND drives are on the market&lt;p&gt;Who has enough money to get a mutli-TB SSD for SOHO?!</text></item></parent_chain></comment><story><title>ZFS Is the Best Filesystem For Now</title><url>http://blog.fosketts.net/2017/07/10/zfs-best-filesystem-now/</url></story>