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EMC Host Connectivity with QLogic FC and iSCSI HBAs and FCoE CNAs for the Linux Environment
Additional Notes
Device reconfiguration: Device numbering
In the Linux kernel, the SCSI addresses are not used in the device
names as they are in other types of UNIX (Sun, SGI, HP-UX, and BSD,
for example). Block device filenames take the form
/dev/sd ln,
where
l is the letter denoting the physical drive and n is the number
denoting the partition on that physical drive. Disk device file names
and major and minor numbers are assigned dynamically at boot time
or device loading time in the order of discovery.
Depending upon the hardware configuration, if a device is added
and the system rebooted, the device numbering might change,
possibly rendering the host's mount table inaccurate. For the most
consistent results and to reduce the possibility of mount table
inaccuracies, new devices should be appended (if possible) to the list
of already attached devices. For example, if the host contains multiple
adapters, it would be best to append the new device to the last
adapter and to the end of the device list attached to that adapter. This
would eliminate the need to alter the preexisting entries in the mount
table, since the new device could be appended to that as well.
If a new device were added to the first out of two adapters and the
system rebooted, the devices all shift by one number and the mount
table entries would also need to be shifted by one device. If there is
only one adapter, the new device can more easily be appended to the
list of the regularly attached devices and the mount table altered
accordingly.