Difference: FibreAttach (4 vs. 5)

Revision 52009-05-12 - ascobie

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Attaching a linux box to a SAN

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  1. Check the profile is compiled and received by machine.
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  1. Reboot the machine. This reboot will compile the qlogic driver module for the current kernel. It will then trigger an additional reboot.
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  1. Reboot the machine. This reboot will compile the qlogic driver module for the current kernel. It will then trigger an additional reboot (Step not required for SL5)
 
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If you have just added a new volume to an array, you will probably need to get the HBA to rescan the bus to detect it. For QLogic cards, the following should work

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echo "scsi-qlascan" > /proc/scsi/qla2xxx/1 echo "- - -" > /sys/class/scsi_host/host/scan or rescan-scsi-bus.sh -c -l -w
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echo "- - -" > /sys/class/scsi_host/host_id_/scan
 
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Though you will have to use the path appropriate to your HBA and port in use. And obtain the rescan-scsi-bus.sh script from the web.
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Though you will have to use the path appropriate to your HBA and port in use. For multipath you will need to do this for each port.
 
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Under FC5, the SCSI stack now creates a soft link to each partition it finds on any attached disk (volume), whether it be local or on a SAN, in the /dev/disk/by-id directory. These soft links are based on the unique SCSI identifiers for the associated volumes. In effect, the SCSI stack is now automatically doing the work that the FC3 udev service did, with no configuration required; with the slight difference that the links are now per partition rather than being per disk (volume).
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Since FC5, the SCSI stack creates a soft link to each partition it finds on any attached disk (volume), whether it be local or on a SAN, in the /dev/disk/by-id directory. These soft links are based on the unique SCSI identifiers for the associated volumes. In effect, the SCSI stack is now automatically doing the work that the FC3 udev service did, with no configuration required; with the slight difference that the links are now per partition rather than being per disk (volume).
  In the following example, there are five volumes, the first three of which have just one partition, the fourth has two partitions and the fifth has currently no partitions :-
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  • The <lcfg/options/multipath.h> header enables multipath support. Note that no multipath configuration is yet possible; a component may be written in the future if it proves necessary. (Remember to use <dice/options/multipath.h> under DICE)
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  • If you are using a qlogic HBA, you must disable the driver's failover option (This is disabled by default for DICE)
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  • If you are using a qlogic HBA and the qlogic supplied driver, you must disable the driver's failover option (The default is to use the stock kernel driver)
 
  • The storage array must export the LUNs you want to access on all fibre paths. To avoid confusion, it's a very good idea to have the LUNs map to the same volumes on each path; otherwise it is very tricky to identify which volume is which.
  • The multipath system presents the storage volumes and partitions under /dev/mpath rather than under /dev/disk/by-id, and without a scsi prefix. The volumes are still presented under /dev/disk/by-id, but you should not use these devices as they are hard-wired to one fibre path and will not failover if that path fails.
  • Use the /sbin/multipath -l command to list the available volumes, instead of /sbin/lsscsi and /sbin/scsi_id used in the above instructions. Where there are many storage arrays connected, it will still be necessary to use /sbin/scli to identify the array required (as documented above).
 
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