Limitations of RDM LUNs managed by SnapDrive
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SnapDrive has a few limitations for provisioning RDM LUNs. You must be aware of the limitations that might affect your environment.
An RDM LUN cannot serve either as a boot disk or system disk.
SnapDrive does not support RDM LUNs in Internet Small Computer System Interface (iSCSI) environments.
SnapDrive does not support MPIO in the guest operating system, although VMware ESX server supports MPIO.
When the transport protocol is
FC, the igroup that is specified in the CLI command is ignored by SnapDrive, and the igroup is automatically created by the virtual interface.
You can rename, move, or delete the
/usr/bin/rescan-scsi-bus.shscript that is bundled as part of
sg3_utilsto avoid limiting the number of RDM LUNs to eight.
If you want to retain
sg3_utilsand avoid limiting the number of RDM LUNs to eight, then you must create a wrapper script
/root/dynamic-lun-rescan.shand from that script run
/usr/bin/rescan-scsi-bus.sh, with the options
-rand assign full permissions.
The following is an example of the modified content of
#cat /root/dynamic-lun-rescan.sh #Wrapper script used to call the actual rescan script. /usr/bin/rescan-scsi-bus.sh -w -c -r
Limitations related to VMware ESX server
Each guest operating system can be configured with four SCSI controllers, and each SCSI controller can be mapped to 16 devices.
However, one device is reserved per controller, and therefore a total of 60 (16 *4 — 4) RDM LUNs can be mapped to the guest operating system.
Each ESX server can be mapped to a maximum of 256 RDM LUNs.