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If a Logical Volume Manager (LVM) volume group includes a device running Hitachi Dynamic Link Manager (HDLM) Software, you must disable the LVM cache file settings. If you do not disable the LVM cache file settings, the volume group might be activated on a SCSI device rather than an HDLM device. As a result, when the volume group is accessed, the volume group will not operate in a multi-path configuration.NOTE: This issue does not occur in a volume group used for a boot disk.The HDLM device is created normally, and the results displayed by commands such asdlmcfgmgr -vare correct. The LVM command displays the volume group as if the volume group is activated on an HDLM device.In this situation, the following message is output to the console when a volume group is activated.Example output message:Found duplicate PV <physical-volume> : using <non-HDLM-device> not /dev/sddlmNNNOTE: If the device name at the end of the message is the name of a SCSI device and not an HDLM device, there is no issue even if the message is output.This issue occurs when the following conditions are met:The LVM cache file settings are enabled.1 is specified forwrite_cache_statein the following configuration file:/etc/lvm/lvm.confThe LVM volume group includes an HDLM device.NOTE: This issue does not occur in a volume group that contains a boot disk.To confirm whether the symptoms are present, perform the following steps:Check mapping information for the volume group by using the dmsetup deps -o blkdevname command. The information is displayed by the device name or the major and minor numbers for the device file, depending on the OS version. If names are displayed, proceed to step 3. If numbers are displayed, perform the following steps:Example:# dmsetup deps -o blkdevname<volume-group-name>-<logical-volume-name> : <x> dependencies : <device-name>or<volume-group-name>-<logical-volume-name> : <x> dependencies : < major number , minor number >Check the device names or major and minor numbers for each logical volume. The value ofXindicates the number of disks configured for the logical volume, and does not relate to this issue.Check the device file name corresponding to the major and minor numbers displayed in the/proc/partitionsinformation.Example:# /bin/cat /proc/partitionsmajor minor #blocks name(major number) (minor number) (physical disk block count) (device name)By using thedlmcfgmgr -vcommand, confirm the HDLM device and the SCSI device names being managed by HDLM.Example:# dlmcfgmgr -vHDevName Management Device Host Channel Target Lun/dev/sddlmaa configured /dev/sdb 1 0 0 0/dev/sdf 1 0 1 0/dev/sdj 9 0 0 0/dev/sdn 9 0 1 0Example:HDLM device : sddlmaaSCSI devices managed by HDLM : sdb, sdf, sdj, sdnCheck whether any of the "SCSI devices to be managed" verified in step 3 are included in step 1 or step 2 for the device names identified in step 3. If any of them are included in the output, the corresponding volume group will not operate in a multi-path configuration.Even if the issue does not occur during this check, the issue might still occur if you reboot a host, or activate the volume group by using thevgchangecommand. Refer to theResolutionsection and disable the LVM cache file settings.This issue is due to a defect in the HDLM documentation. If you enable the LVM cache file settings, the device configuration list is stored in the LVM cache file when the file is updated.
This issue affects Hitachi Dynamic Link Manager Software for Linux 6.5.2-00 or later.
The device configuration on a server changes when the server starts, if a path is disconnected or connected, or when other changes occur; however, changes in the device configuration are not linked with the timing of updates to the LVM cache file. Therefore, the contents of the LVM cache file and the server configuration might become inconsistent.If multiple device files are present for a physical volume, such as within a multi-path environment, the SCSI device is selected as a physical volume instead of the HDLM device when you activate the volume group while the latest device configuration and the content of the LVM cache file do not match.For these reasons, if the HDLM device is included in an LVM volume group, you must disable the LVM cache file settings. This information was not included in theHitachi Dynamic Link Manager Software User Guide.If the LVM cache file settings are enabled, and the issue of not operating as a multi-path configuration occurs, then perform the following steps to resolve the issue (during these steps, the target volume group might temporarily become inaccessible):In addition, it takes more time to activate the volume group when the LVM cache file settings are disabled.Clear the LVM cache:# rm /etc/lvm/cache/.cacheDisable the LVM cache functionality: Specify0forwrite_cache_statein the following configuration file:/etc/lvm/lvm.confScan the volume group:# vgscanDeactivate the volume group containing the logical volume that is not operating in a multi-path configuration:# vgchange -an <volume-group-name>Reactivate the volume group:# vgchange -ay <volume-group-name>Measurements of the increased time required if you executevgchangeonce in the following environment:CPU: 8Memory: 4GB2-path configuration for an LUA logical volume is created in each of 50 volume groups, andvgchange -ayis measured:Number of LUs256512102420484096Total number of paths5121024204840968192With cache8.5299.20310.76914.28725.718Without cache9.78111.91216.44127.26764.214Time difference (seconds)+1.252+2.709+5.672+12.980+38.718NOTE: You can restart the server instead of performing steps 4 and 5.The product has not been changed to fix this issue because the issue is caused by LVM behavior.Disable the LVM cache file settings by using the following steps. In addition, it takes more time to activate the volume group when the LVM cache file settings are disabled:Clear the LVM cache:# rm /etc/lvm/cache/.cacheDisable the LVM cache functionalit: Specify0forwrite_cache_statein the following configuration file:/etc/lvm/lvm.confScan the volume group:# vgscanFor details regarding the increased time required to activate the volume group, refer to the section beginning with "If the LVM cache file settings are enabled...".RECEIVE PROACTIVE UPDATES: Receive support alerts (such as Customer Advisories), as well as updates on drivers, software, firmware, and customer replaceable components, proactively in your e-mail through HPE Subscriber's Choice. Sign up for Subscriber's Choice at the following URL:Proactive Updates Subscription Form
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