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Snapdrive for Unix

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 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.sh script that is bundled as part of sg3_utils to avoid limiting the number of RDM LUNs to eight.

    Note If you want to retain /usr/bin/rescan-scsi-bus.sh in sg3_utils and avoid limiting the number of RDM LUNs to eight, then you must create a wrapper script /root/dynamic-lun-rescan.sh and from that script run /usr/bin/rescan-scsi-bus.sh, with the options -w, -c, and -r and 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

  • 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.

Related information

Guest OS preparation for installing SnapDrive for UNIX

VMware VMotion support in SnapDrive for UNIX

Configuring Virtual Storage Console for SnapDrive for UNIX

Considerations for provisioning RDM LUNs

www.vmware.com/pdf/vsphere4/r40/vsp_40_config_max.pdf