<div dir="ltr">I create a <b>4x256GB-SSD RAID0(/dev/md1)</b> and I test the performance through fio.<div>fio config:</div><div><pre class="gmail-code gmail-highlight" style="box-sizing:border-box;overflow-x:auto;overflow-y:hidden;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;padding:10px;margin-top:0px;margin-bottom:0px;word-break:break-all;word-wrap:normal;border-top:none;border-right:none;border-bottom:none;border-left:1px solid rgb(220,224,230);border-radius:0px;font-size:13px;line-height:1.5;color:rgb(51,51,51)"><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span id="gmail-LC2" class="gmail-line" style="box-sizing:border-box;display:inline">ioengine=libaio</span>
<span id="gmail-LC3" class="gmail-line" style="box-sizing:border-box;display:inline">direct=1</span>
<span id="gmail-LC4" class="gmail-line" style="box-sizing:border-box;display:inline">time_based</span>
<span id="gmail-LC5" class="gmail-line" style="box-sizing:border-box;display:inline">runtime=120</span>
<span id="gmail-LC6" class="gmail-line" style="box-sizing:border-box;display:inline">ramp_time=30</span>
<span id="gmail-LC7" class="gmail-line" style="box-sizing:border-box;display:inline">size=100g</span></code></pre></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">The </span></code><span style="font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace">sequential</span><span style="font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace"> </span><span style="background-color:transparent;color:inherit;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit">read/write performance is:</span></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><b><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">read: 2000MB/s<br></span></code><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">write: 1800MB/s</span></code></b></blockquote><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><br></span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">Now I make a ext4 on the RAID0(/dev/md1) and mount on /home/.</span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">ANd I create a 100G-disk.qcow2 by guestfish.</span></code></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">$guestfish<br></span></code><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">><fish>: disk-create disk.qcow2 qcow2 100*1024*1024*1024<br></span></code><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">><fish>: run<br></span></code><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">><fish>: mkfs ext4 /dev/sda<br></span></code><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">><fish>: shutdown<br></span></code><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">><fish>: quit</span></code></blockquote><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">No errors showed.</span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><br></span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">I mount the disk.qcow2 on the /home/test/, and create a 50GB file.</span></code></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">$dd if=/dev/zero of=/home/test/file bs=1M count=51280</span></code></blockquote><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><br></span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">Test sequential read/write again through fio and config almost the same:</span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><pre class="gmail-code gmail-highlight" style="box-sizing:border-box;overflow-x:auto;overflow-y:hidden;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;padding:10px;margin-top:0px;margin-bottom:0px;word-break:break-all;word-wrap:normal;border-top:none;border-right:none;border-bottom:none;border-left:1px solid rgb(220,224,230);border-radius:0px;font-size:13px;line-height:1.5;color:rgb(51,51,51)"><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span id="gmail-LC2" class="gmail-line" style="box-sizing:border-box;display:inline">ioengine=libaio</span>
<span id="gmail-LC3" class="gmail-line" style="box-sizing:border-box;display:inline">direct=1</span>
<span id="gmail-LC4" class="gmail-line" style="box-sizing:border-box;display:inline">time_based</span>
<span id="gmail-LC5" class="gmail-line" style="box-sizing:border-box;display:inline">runtime=120</span>
<span id="gmail-LC6" class="gmail-line" style="box-sizing:border-box;display:inline">ramp_time=30</span>
<span id="gmail-LC7" class="gmail-line" style="box-sizing:border-box;display:inline">size=50g</span></code></pre></span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">and the testing filename is /home/test/file</span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><br></span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">and the performance is :</span></code></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><b><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">read: 86MB/s<br></span></code><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">write: 43MB/s</span></code></b></blockquote><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><br></span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline">how come the performance is so bad? almost down 95%.</span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><br></span></code></div><div><font face="Menlo, Liberation Mono, Consolas, DejaVu Sans Mono, Ubuntu Mono, Courier New, andale mono, lucida console, monospace">My machine is: 4.4.0-83-generic, Ubuntu 16.04, x86_64 GNU/Linux</font></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><br></span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><br></span></code></div><div><code style="box-sizing:border-box;font-family:Menlo,"Liberation Mono",Consolas,"DejaVu Sans Mono","Ubuntu Mono","Courier New","andale mono","lucida console",monospace;font-size:inherit;padding:0px;color:inherit;background-color:transparent;border-radius:0px;word-wrap:normal"><span class="gmail-line" style="box-sizing:border-box;display:inline"><br></span></code></div><div><br></div><div><br></div></div>