{"id":68,"date":"2009-03-01T10:55:09","date_gmt":"2009-03-01T08:55:09","guid":{"rendered":"http:\/\/bergs.biz\/blog\/?p=68"},"modified":"2009-03-01T10:57:29","modified_gmt":"2009-03-01T08:57:29","slug":"startled-by-component-device-mismatches-on-raid1-volumes","status":"publish","type":"post","link":"https:\/\/bergs.biz\/blog\/2009\/03\/01\/startled-by-component-device-mismatches-on-raid1-volumes\/","title":{"rendered":"Startled by &#8220;component device mismatches&#8221; on RAID1 volumes"},"content":{"rendered":"<p>I was startled today by a message in syslog that seems to point to a problem with my RAID1 volumes:<\/p>\n<p><code>Mar\u00a0 1 01:13:54 server mdadm[961]: RebuildFinished event detected on md device \/dev\/md3, component device\u00a0 mismatches found: 512<\/code><\/p>\n<p>This value is reflected in the following counter:<br \/>\n<code>root:\/etc\/mdadm# cat \/sys\/block\/md3\/md\/mismatch_cnt 512<\/code><\/p>\n<p>I tried to clarify this by googling around, but I found no definitive answer whether this is an actual problem or not. However, I found a way to resync the MD components so that no mismatches remain:<\/p>\n<p><code>root:\/etc\/mdadm# <\/code><code>echo repair &gt;&gt; \/sys\/block\/md3\/md\/sync_action<\/code><\/p>\n<p>After you execute the repair you will notice that the counter shows the same number of mismatches again:<\/p>\n<p><code>root:\/etc\/mdadm# cat \/sys\/block\/md3\/md\/mismatch_cnt 512<\/code><\/p>\n<p>This was to be expected &#8212; because the repair corrected (and thus encountered) this number of mismatches. So, if you force a check again, the counter should be down to 0:<\/p>\n<p><code>root:\/etc\/mdadm# echo check &gt;&gt; \/sys\/block\/md3\/md\/sync_action<br \/>\nroot:\/etc\/mdadm# watch cat \/proc\/mdstat<br \/>\n[wait until check is finished]<br \/>\nroot:\/etc\/mdadm# cat \/sys\/block\/md3\/md\/mismatch_cnt<br \/>\n0<br \/>\n<\/code><\/p>\n","protected":false},"excerpt":{"rendered":"<p>I was startled today by a message in syslog that seems to point to a problem with my RAID1 volumes: Mar\u00a0 1 01:13:54 server mdadm[961]: RebuildFinished event detected on md device \/dev\/md3, component device\u00a0 mismatches found: 512 This value is reflected in the following counter: root:\/etc\/mdadm# cat \/sys\/block\/md3\/md\/mismatch_cnt 512 I tried to clarify this by [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[32],"class_list":["post-68","post","type-post","status-publish","format-standard","hentry","category-computers","tag-raid"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.4 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Startled by &quot;component device mismatches&quot; 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