Developers Guide

Volume management
16 Dell EMC SC Series with Red Hat Enterprise Linux 7x | CML1071
The following shows the sample, truncated output from the rescan-scsi-bus.sh script showing a rescan of
the SCSI bus against two host adapter’s (adapter 10 and adapter 8) with no new device found or devices
removed:
# rescan-scsi-bus.sh
Host adapter 10 (iscsi_tcp) found.
Host adapter 8 (iscsi_tcp) found.
Scanning SCSI subsystem for new devices
Scanning host 8 for all SCSI target IDs, all LUNs
Scanning for device 8 0 0 1 ...
OLD: Host: scsi8 Channel: 00 Id: 00 Lun: 01
Vendor: COMPELNT Model: Compellent Vol Rev: 0702
Type: Direct-Access ANSI SCSI revision: 05
Scanning host 10 for all SCSI target IDs, all LUNs
Scanning for device 10 0 0 1 ...
OLD: Host: scsi10 Channel: 00 Id: 00 Lun: 01
Vendor: COMPELNT Model: Compellent Vol Rev: 0702
Type: Direct-Access ANSI SCSI revision: 05
0 new device(s) found.
0 device(s) removed.
2.8 Removing volumes
Linux stores information about each volume presented to it. Even if a volume is in an unmapped state on the
SC Series storage, Linux will retain information about that volume until the next reboot. If Linux is presented
with a volume from the same target using the same LUN ID prior to any reboot, it will reuse the old data about
that volume. This may result in misinformation and mismanagement of the volumes and potentially impact
data integrity in the business environment.
It is recommended to always unmount, remove, and delete all volume information on Linux after the volume is
deemed no longer in use. This management of the Linux volume metadata is non-destructive to any actual
data stored on the volume itself.
The process for removing multipath volumes is outlined in the following steps.
1. Quiesce any I/O to the mounted volume.
2. Unmount the volume.
3. Edit /etc/multipath.conf and remove any syntax referencing this volume.
4. Reload the multipathd daemon (systemctl restart multipathd.service).
5. Remove the multipath backing device files by running the following script.
6. Remove any mappings to the volume(s) from SC Series storage.
The rescan-scsi-bus.sh script (included in the sg3_utils.x86_64 package) with the –r flag can be used to
rescan the SCSI bus to remove devices from the host.
To remove single volumes (not managed by multipath) use the following steps.
1. Quiesce any I/O to the mounted volume.
2. Unmount the volume.
3. From the command prompt, execute:
# echo 1 > /sys/block/sdX/device/delete