Quite some time ago, I came across a quite hard to find issue during a consulting engagement, which i find worth mentioning. A 2 node RAC cluster running on RHEL4 x86-64 was relocated to a different data center. Apart from making sure, that the switch ports and Fibre Channel Ports are available on the new location, there is not much to worry about.<\/p>\n
After the relocation, on one node the multipathing configuration, implemented with dev-mapper-multipath would not work. The command “multipath -ll” would just not return any output. After more than an hour, we pinned the issue down to the error message:<\/p>\n
# multipath -v 3
\n#
\n# all paths in cache :
\n#
\n…
\n…
\n…
\npath sdh not found in pathvec<\/p><\/blockquote>\nWhen checking what device sdh was, we realized that this was a KVM device, plugged in by the sysadmins. <\/p>\n
\nMay 27 14:46:26 host1 kernel: Attached scsi removable disk sdh at scsi10, channel 0, id 0, lun 0
\nMay 27 14:46:26 host1 kernel: Type: Direct-Access ANSI SCSI revision: 02
\nMay 27 14:46:26 host1 kernel: Vendor: KVM Model: vmDisk Rev: 0.01
\nMay 27 14:46:26 host1 kernel: scsi10 : SCSI emulation for USB Mass Storage devices
\nMay 27 14:46:26 host1 kernel: sr1: scsi3-mmc drive: 0x\/0x caddy
\nMay 27 14:46:26 host1 kernel: Type: CD-ROM ANSI SCSI revision: 02
\nMay 27 14:46:26 host1 kernel: Vendor: KVM Model: vmDisk-CD Rev: 0.01\n<\/p><\/blockquote>\n\nBTW: What is a KVM device?<\/strong>
Wikipedia states: A KVM switch (with KVM being an abbreviation for Keyboard, Video or Visual Display Unit, Mouse) is a hardware device that allows a user to control multiple computers from a single keyboard, video monitor and mouse.<\/p><\/blockquote>\nWe then added the device sdh to the multipath blacklist section in \/etc\/multipath.conf, and the problem was solved:<\/p>\n
devnode_blacklist {
\ndevnode “^sdh$”
\n}<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"Quite some time ago, I came across a quite hard to find issue during a consulting engagement, which i find worth mentioning. A 2 node RAC cluster running on RHEL4 x86-64 was relocated to a different data center. Apart from making sure, that the switch ports and Fibre Channel Ports are available on the new […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[44,49,5,35],"tags":[],"class_list":["post-728","post","type-post","status-publish","format-standard","hentry","category-linux-unix-2","category-linux-itanium","category-oracle-database","category-real-application-clusters-oracle-database-2"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/posts\/728","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/comments?post=728"}],"version-history":[{"count":7,"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/posts\/728\/revisions"}],"predecessor-version":[{"id":735,"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/posts\/728\/revisions\/735"}],"wp:attachment":[{"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/media?parent=728"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/categories?post=728"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ora-solutions.net\/web\/wp-json\/wp\/v2\/tags?post=728"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}