User manual NOVELL ENTERPRISE LINUX 5.5 ONLINE STORAGE GUIDE

[. . . ] Red Hat Enterprise Linux 5. 5 Online Storage Guide For Red Hat Enterprise Linux 5 Red Hat Enterprise Linux Engineering Mike Christie Tom Coughlan Don Domingo Rob Evers Development Community Pasi Kärkkäinen Abstract This document outlines the different procedures involved in reconfiguring storage devices while the system is running. The document currently addresses iSCSI and Fibre Channel interconnects. Other interconnects may be added in future versions of this document. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] Open /etc/sysconfig/network-scripts/ifcfg-eth3. 101. Edit it to ensure that the following settings are configured accordingly: DEVICE=eth3. 101 VLAN=yes ONBOOT=yes 3. Start the data center bridging daemon (dcbd) using the following command: /etc/init. d/dcbd start 4. Use the dcbtool utility to enable data center bridging and FCoE on the ethernet interface using the following commands: dcbtool sc eth3 dcb on dcbtool sc eth3 app:fcoe e:1 These commands will only work if no other changes have been made to the dcbd settings for the ethernet interface. 5. Start FCoE using the command /etc/init. d/fcoe start. The fibre-channel device should appear shortly, assuming all other settings on the fabric are correct. After correctly configuring the ethernet interface to use FCoE, Red Hat recommends that set FCoE and dcbd to run at startup. To do so, use chkconfig, as in: chkconfig dcbd on chkconfig fcoe on 9. Scanning Storage Interconnects There are several commands available that allow you to reset and/or scan one or more interconnects, potentially adding and removing multiple devices in one operation. This type of scan can be disruptive, as it can cause delays while I/O operations timeout, and remove devices unexpectedly. As such, 14 iSCSI Discovery Configuration Red Hat recommends that this type of scan be used only when necessary. In addition, the following restrictions must be observed when scanning storage interconnects: 1. All I/O on the effected interconnects must be paused and flushed before executing the procedure, and the results of the scan checked before I/O is resumed. As with removing a device, interconnect scanning is not recommended when the system is under memory pressure. To determine the level of memory pressure, run the command vmstat 1 100; interconnect scanning is not recommended if free memory is less than 5% of the total memory in more than 10 samples per 100. It is also not recommended if swapping is active (non-zero si and so columns in the vmstat output). The command free can also display the total memory. The following commands can be used to scan storage interconnects. echo "1" > /sys/class/fc_host/host/issue_lip This operation performs a Loop Initialization Protocol (LIP) and then scans the interconnect and causes the SCSI layer to be updated to reflect the devices currently on the bus. A LIP is, essentially, a bus reset, and will cause device addition and removal. This procedure is necessary to configure a new SCSI target on a Fibre Channel interconnect. Bear in mind that issue_lip is an asynchronous operation. The command may complete before the entire scan has completed. You must monitor /var/log/messages to determine when it is done. The lpfc and qla2xxx drivers support issue_lip. For more information about the API capabilities supported by each driver in Red Hat Enterprise Linux, refer to Table 1, "Fibre-Channel API Capabilities". [. . . ] When the error handler is triggered, it attempts the following operations in order (until one successfully executes): 1. If all of these operations fail, the device will be set to the offline state. When this occurs, all IO to that device will be failed, until the problem is corrected and the user sets the device to running. The process is different, however, if a device uses the fibre channel protocol and the rport is blocked. [. . . ]