Dell Emulex Family of Adapters - Manual (Page 979)

Emulex Drivers Version 10.2 for Linux User Manual P010081-01A Rev. A
Appendix F. lpfc Driver BlockGuard Functionality
Enabling BlockGuard
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typically passed as the Guard Tag between the Initiator Host and the HBA. The HBA
hardware will translate the IP Checksum into a CRC, or visa versa, on data being
sent/received on the wire. The CRC is called a DIF protection type, and the IP
Checksum is referred to as DIX protection type.
Enabling BlockGuard
BlockGuard is disabled by default. To enable it, the parameter lpfc_enable_bg must be
passed to the driver as follows:
insmod lpfc.ko lpfc_enable_bg=1
For a permanent configuration that will persist across system reboots, create the file
/etc/modprobe.d/lpfc
and place the following line into it:
options lpfc lpfc_enable_bg=1
Additional module parameters may be added to this line, separated by spaces.
SCSI Command Support
SCSI Operation Codes
When there are both READ and WRITE requests, the command descriptor block (CDB)
passed to the HBA from the Initiator Host has a read protect/write protect
(RDPROTECT/WRPROTECT) field which indicates to the target whether data
integrity verification is to be performed. It also indicates whether to transfer protection
data between initiator and target. The HBA does not know if a target supports
protection information or which type of protection it is formatted with. The Initiator
Host, which has this knowledge, will always prepare a CDB with the appropriate
RDPROTECT/WRPROTECT information, depending on target format and capabilities.
The request will also include information about which protection type the target has
been formatted with.
In addition, the Initiator Host will also provide the HBA with an operation code which
tells the controller how to place the protection data for the type of I/O to perform. Each
I/O is logically a two-step process. The data is transferred between the Initiator Host
and the HBA (over the PCI Bus) and between the HBA and the target (over the SAN)
(see Figure F-2). The type of operation defines whether the data transfer has protection
data or not.