Dell PowerVault MD3220i Owner's Manual - Page 185
Troubleshooting
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• I/O may hang when a Device Mapper device is deleted before the volume is unmounted. • If the scsi_dh_rdac module is not included in initrd, slower device discovery may be seen and the syslog may become populated with buffer I/O error messages. • I/O may hang if the host server or storage array is rebooted while I/O is active. All I/O to the storage array should be stopped before shutting down or rebooting the host server or storage array. • With the MD3200i Series array, after a failed path is restored, failback does not occur automatically because the driver cannot auto-detect devices without a forced rescan. Run the command rescan_dm_devs to force a rescan of the host server. This restores the failed paths enabling failback to occur. • Failback can be slow when the host system is experiencing heavy I/O. The problem is exacerbated if the host server is also experiencing very high CPU utilization. • The Device Mapper Multipath service can be slow when the host system is experiencing heavy I/O. The problem is exacerbated if the host server is also experiencing very high CPU utilization. • If the root disk is not blacklisted in the multipath.conf file, a multipathing node may be created for the root disk. The command multipath -ll lists vendor/product ID which can help identify this issue. Troubleshooting Question How can I check if multipathd is running? Answer Run the following command. /etc/init.d/multipathd status Configuration: Device Mapper Multipath for Linux 185
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