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Reviewed-by: Miskanin, Jan <jan.miskanin@t-systems.com> Co-authored-by: zhangyue <zhangyue164@huawei.com> Co-committed-by: zhangyue <zhangyue164@huawei.com>
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86 lines
9.0 KiB
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<a name="evs_faq_0080"></a><a name="evs_faq_0080"></a>
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<h1 class="topictitle1">Why Does My Disk Performance Test Using Fio Have Incorrect Results?</h1>
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<div id="body8662426"><div class="section" id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_section690984914297"><h4 class="sectiontitle">Symptom</h4><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p781618547294">You have followed the test performance method, but the test results do not meet expectations.</p>
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</div>
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<div class="section" id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_section192121013163019"><h4 class="sectiontitle">Troubleshooting</h4><p id="evs_faq_0080__en-us_topic_0000001073763031_p4506152545613">During a disk performance test, the disk and stress test conditions play an important role.</p>
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<p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p17987205213470">Possible causes are listed here in order of their probability.</p>
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<p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p997211345215">If the fault persists after you have ruled out one cause, move on to the next one in the list.</p>
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<div class="notice" id="evs_faq_0080__en-us_topic_0000001073763031_note1674474613187"><span class="noticetitle"><img src="public_sys-resources/notice_3.0-en-us.png"> </span><div class="noticebody"><p id="evs_faq_0080__en-us_topic_0000001073763031_p97441546121817">Some operations may result in data loss. It is recommended that you use raw disks for performance test.</p>
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</div></div>
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<div class="fignone" id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_fig58223406246"><span class="figcap"><b>Figure 1 </b>Troubleshooting</span><br><span><img id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_image198221040192414" src="en-us_image_0000001080217203.png"></span></div>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_table11639162722113" frame="border" border="1" rules="all"><caption><b>Table 1 </b>Troubleshooting</caption><thead align="left"><tr id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_row563912711214"><th align="left" class="cellrowborder" valign="top" width="31.290000000000003%" id="mcps1.3.2.7.2.3.1.1"><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p17639192710215">Possible Cause</p>
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</th>
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<th align="left" class="cellrowborder" valign="top" width="68.71000000000001%" id="mcps1.3.2.7.2.3.1.2"><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p1063918274214">Solution</p>
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</th>
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</tr>
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</thead>
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<tbody><tr id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_row1163911274215"><td class="cellrowborder" valign="top" width="31.290000000000003%" headers="mcps1.3.2.7.2.3.1.1 "><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p1663915273217">The partition's start sector number is not 4-KiB aligned.</p>
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</td>
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<td class="cellrowborder" valign="top" width="68.71000000000001%" headers="mcps1.3.2.7.2.3.1.2 "><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p126399272210">Go to <a href="#evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_section83925230328">Check Whether Partition's Start Sector Number Is 4-KiB Aligned</a>.</p>
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<p id="evs_faq_0080__en-us_topic_0000001073763031_p4117130103112">Delete the partition and select a 4-KiB aligned start sector number for the new partition.</p>
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</td>
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</tr>
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<tr id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_row76394277211"><td class="cellrowborder" valign="top" width="31.290000000000003%" headers="mcps1.3.2.7.2.3.1.1 "><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p6639112762113">The disk used in testing was not a raw disk.</p>
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</td>
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<td class="cellrowborder" valign="top" width="68.71000000000001%" headers="mcps1.3.2.7.2.3.1.2 "><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p1063962762110">Purchase an empty disk and attach it to a <span id="evs_faq_0080__en-us_topic_0000001073763031_text18435711143314">server</span> for testing.</p>
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</td>
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</tr>
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<tr id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_row1063915276211"><td class="cellrowborder" valign="top" width="31.290000000000003%" headers="mcps1.3.2.7.2.3.1.1 "><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p11639102752118">Stress test conditions were not properly set.</p>
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</td>
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<td class="cellrowborder" valign="top" width="68.71000000000001%" headers="mcps1.3.2.7.2.3.1.2 "><p id="evs_faq_0080__en-us_topic_0000001073763031_p61421537183810">Configure multi-core processing and arrange queues properly to maximize the concurrent performance.</p>
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</td>
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</tr>
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<tr id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_row13639142722110"><td class="cellrowborder" valign="top" width="31.290000000000003%" headers="mcps1.3.2.7.2.3.1.1 "><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p56391927182115">An inappropriate data block size was used.</p>
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</td>
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<td class="cellrowborder" valign="top" width="68.71000000000001%" headers="mcps1.3.2.7.2.3.1.2 "><p id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_p6639112713211">Set a suitable data block size.</p>
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<ul id="evs_faq_0080__en-us_topic_0000001073763031_ul10879247151911"><li id="evs_faq_0080__en-us_topic_0000001073763031_li12879647141917">When testing the disk IOPS, set the data block size to a small value, for example, 4 KiB.</li><li id="evs_faq_0080__en-us_topic_0000001073763031_li58261651132015">When testing the disk throughput, set the data block size to a large value, for example, 1024 KiB.</li></ul>
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</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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<div class="section" id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_section83925230328"><a name="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267670624_section83925230328"></a><a name="en-us_topic_0000001073763031_en-us_topic_0267670624_section83925230328"></a><h4 class="sectiontitle">Check Whether Partition's Start Sector Number Is 4-KiB Aligned</h4><ol id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267243048_ol188038271012"><li id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267243048_li7803162171014"><span>Log in to the server and switch to user <strong id="evs_faq_0080__b376111202496">root</strong>.</span></li><li id="evs_faq_0080__en-us_topic_0000001073763031_en-us_topic_0267243048_li63928616107"><span>Before you start the test, run the following command to check whether the start sector number is 4-KiB aligned:</span><p><p id="evs_faq_0080__evs_faq_0019_p3208370595643"><strong id="evs_faq_0080__evs_faq_0019_b4011626921454">fdisk -lu</strong></p>
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<div class="p" id="evs_faq_0080__evs_faq_0019_p1786333621454">Information similar to the following is displayed:<pre class="screen" id="evs_faq_0080__evs_faq_0019_screen1689789621454">[root@ecs-centos sdc]# fdisk -lu
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Disk /dev/xvda: 10.7 GiB, 10737418240 bytes, 20971520 sectors
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Units = sectors of 1 * 512 = 512 bytes
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Sector size (logical/physical): 512 bytes / 512 bytes
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I/O size (minimum/optimal): 512 bytes / 512 bytes
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Disk label type: dos
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Disk identifier: 0x7db77aa5
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Device Boot Start End Blocks Id System
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/dev/xvda1 * 2048 20968919 10483436 83 Linux
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Disk /dev/xvdb: 10.7 GiB, 10737418240 bytes, 20971520 sectors
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Units = sectors of 1 * 512 = 512 bytes
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Sector size (logical/physical): 512 bytes / 512 bytes
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I/O size (minimum/optimal): 512 bytes / 512 bytes
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Disk /dev/xvdc: 53.7 GiB, 53687091200 bytes, 104857600 sectors
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Units = sectors of 1 * 512 = 512 bytes
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Sector size (logical/physical): 512 bytes / 512 bytes
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I/O size (minimum/optimal): 512 bytes / 512 bytes
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Disk label type: dos
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Disk identifier: 0x3cf3265c
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Device Boot Start End Blocks Id System
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/dev/xvdc1 2048 41943039 20970496 83 Linux</pre>
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</div>
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<ul id="evs_faq_0080__evs_faq_0019_ul325244321454"><li id="evs_faq_0080__evs_faq_0019_li2655229721454">If 8 can be divided by the start sector number, the number is 4-KiB aligned.</li><li id="evs_faq_0080__evs_faq_0019_li3764408421454">If 8 cannot be divided by the start sector number, the number is not 4-KiB aligned. Delete the partition and select a 4-KiB aligned start sector number for the new partition before continuing the test.<div class="notice" id="evs_faq_0080__evs_faq_0019_note59778303152414"><span class="noticetitle"><img src="public_sys-resources/notice_3.0-en-us.png"> </span><div class="noticebody"><p id="evs_faq_0080__evs_faq_0019_p1133816152414">If you delete the partition and select another start sector number for 4-KiB alignment, you will lose all the data on that partition. Exercise caution when performing this operation.</p>
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</div></div>
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</li></ul>
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</p></li></ol>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="evs_01_0080.html">Performance</a></div>
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</div>
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</div>
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