Options for SCSI device scanning

Knowledgebase

Options for SCSI device scanning

On a Linux system SCSI devices are usually detected automatically upon boot or once the respective driver module for the SCSI controller is loaded. Under certain circumstances this detection might fail or not be completely correct. You can therefore influence the SCSI device scanning with kernel parameters.

Parameters

Note: These parameters have to be given as options to the kernel when it is booted. You can either do that manually within the boot menu or enter the options into your boot loader configuration. Please refer to the respective manuals for the needed steps.

The parameters listed in here were first introduced in SLES8 ServicePack 3. They enable runtime tuning, blacklist, probes etc.:

llun_blklst=C,B,T[,C,B,T[,C,B,T[,...]]]

Adds devices, addressed by host adapter no (C), bus number (B, normally 0) and Target ID(T) to the blacklist with BLIST_LARGELUN | BLIST_SPARSELUN. This helps to detect LUNs above 7 on devices reporting as SCSI-2. It also allows LUNs to be nonconsecutive for the devices addressed with this parameter.

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scsi_sparselun=1

Globally assumes the LUNs numbering may be non-consecutive. Potentially increases the scanning time, but makes sure all LUNs of a target are detected.

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scsi_largelun=1

Globally assumes devices can have LUNs larger than 7, independent of the SCSI version they report. Normally, only SCSI-3 devices should have LUNs larger than 7.

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scsi_noreportlun=1

For SCSI-3 devices the REPORT_LUN command is used to avoid the need for a serial scan and thus avoid problems with non-consecutive LUNs. This can be switched off with this parameter, which is needed in case the LUN mapping of the host adapter and the Linux are different. For the zfcp adapter, REPORT_LUN is not used.

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scsi_reportlun2=1

Also try REPORT_LUN for SCSI devices that report as SCSI-2 and are connected to a host adapter that supports more than 8 LUNs per target.

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scsi_allow_ghost_devices=N

This allows to access LUNs with a unit number smaller than N to be accessed despite it reporting as offline. This is needed for some EMC storage devices.

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scsi_inq_timeout=N

This allows to set the SCSI scanning timeout in seconds. Some broken hardware needs larger values than the default of 6. There's one SCSI to IDE converter known to need 25. The default on ppc64 is 25.

Changes from SLES8 SP3 to SLES9

For SLES9 now these settings have changed. You will get an informational message about the option beeing deprecated. linuxrc will however apply the setting. It is advised to use the new options for SLES9:

SLES8 SP3	SLES9
scsi_reportlun2=1	scsi_mod.default_dev_flags=0x20000
scsi_noreportlun=1	scsi_mod.default_dev_flags=0x40000
scsi_sparselun=1	scsi_mod.default_dev_flags=0x40
scsi_largelun=1	scsi_mod.default_dev_flags=0x200
llun_blklst=C,B,T[,C,B,T[,C,B,T[,...]]]	scsi_mod.dev_flags=VENDOR:MODEL:0x240[,V:M:0x240[,...]]

Disclaimer

The origin of this information may be internal or external to Novell. While Novell makes all reasonable efforts to verify this information, Novell does not make explicit or implied claims to its validity.