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:

# multipath -v 3
#
# all paths in cache :
#
…
…
…
path sdh not found in pathvec

When checking what device sdh was, we realized that this was a KVM device, plugged in by the sysadmins.

May 27 14:46:26 host1 kernel: Attached scsi removable disk sdh at scsi10, channel 0, id 0, lun 0
May 27 14:46:26 host1 kernel: Type: Direct-Access ANSI SCSI revision: 02
May 27 14:46:26 host1 kernel: Vendor: KVM Model: vmDisk Rev: 0.01
May 27 14:46:26 host1 kernel: scsi10 : SCSI emulation for USB Mass Storage devices
May 27 14:46:26 host1 kernel: sr1: scsi3-mmc drive: 0x/0x caddy
May 27 14:46:26 host1 kernel: Type: CD-ROM ANSI SCSI revision: 02
May 27 14:46:26 host1 kernel: Vendor: KVM Model: vmDisk-CD Rev: 0.01

BTW: What is a KVM device?
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.

We then added the device sdh to the multipath blacklist section in /etc/multipath.conf, and the problem was solved:

devnode_blacklist {
devnode “^sdh$”
}