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Oracle Linux: How to Configure Oracle Linux to Support 1024 LUNs (Doc ID 1533686.1)

Last updated on NOVEMBER 03, 2023

Applies to:

Oracle Cloud Infrastructure - Version N/A and later
Linux OS - Version Oracle Linux 4.4 to Oracle Linux 6.9 with Unbreakable Enterprise Kernel [4.1.12] [Release OL4U4 to OL6U9]
Oracle VM - Version 3.0.3 and later
Linux x86-64
Linux x86


There are several limits in the Linux kernel and the storage protocols that affect the number of LUNs that can be addressed on a single target.

 - It depends on the transport. Fibre Channel (FC) and iSCSI support lots of LUNs, parallel SCSI does not.

 - It depends on the programming Host Bus Adapter (HBA)'s interface. Even through the FC protocol itself supports huge LUN counts, the HBA interfaces generally do not expose the full 8-byte LUN ID. Each HBA driver has a module parameter that can be tweaked     up to a certain limit. Typically somewhere between 256 and 16K.

 - The SCSI layer also has a limit which can be tweaked via a module parameter. That limit is there because not all devices support the REPORT LUNS command. And we do not want to incrementally scan every target for millions of LUNs. So by default it is capped       at 512. "systool" command will give the number of maximum LUNs. It is provided by "sysfsutils" package.



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