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Chapter 30. Removing a Path to a Storage Device
If you are removing a path to a device that uses multipathing (without affecting other paths to the device), then the general procedure is as follows:
Procedure 30.1. Removing a Path to a Storage Device
- Remove any reference to the device's path-based name, like
/dev/sdor/dev/disk/by-pathor themajor:minornumber, in applications, scripts, or utilities on the system. This is important in ensuring that different devices added in the future will not be mistaken for the current device. - Take the path offline using
echo offline > /sys/block/sda/device/state.This will cause any subsequent I/O sent to the device on this path to be failed immediately. Device-mapper-multipath will continue to use the remaining paths to the device. - Remove the path from the SCSI subsystem. To do so, use the command
echo 1 > /sys/block/device-name/device/deletewheredevice-namemay besde, for example (as described in Procedure 29.1, “Ensuring a Clean Device Removal”).
After performing Procedure 30.1, “Removing a Path to a Storage Device”, the path can be safely removed from the running system. It is not necessary to stop I/O while this is done, as device-mapper-multipath will re-route I/O to remaining paths according to the configured path grouping and failover policies.
Other procedures, such as the physical removal of the cable, followed by a rescan of the SCSI bus to cause the operating system state to be updated to reflect the change, are not recommended. This will cause delays due to I/O timeouts, and devices may be removed unexpectedly. If it is necessary to perform a rescan of an interconnect, it must be done while I/O is paused, as described in Chapter 34, Scanning Storage Interconnects.
