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.
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An RDM LUN cannot serve either as a boot disk or system disk.
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SnapDrive does not support RDM LUNs in Internet Small Computer System Interface (iSCSI) environments.
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SnapDrive does not support MPIO in the guest operating system, although VMware ESX server supports MPIO.
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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 ofsg3_utilsto avoid limiting the number of RDM LUNs to eight.
If you want to retain /usr/bin/rescan-scsi-bus.shinsg3_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-w,-c, and-rand assign full permissions.
The following is an example of the modified content of /root/dynamic-lun-rescan.sh:
#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
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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.
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Each ESX server can be mapped to a maximum of 256 RDM LUNs.
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