Hi All, I've been chasing down a problem with LUN masking on CentOS5/RHEL5 hosts with QLogic HBA's for a few hours and seem to have got to an impass; Any device (disks in my case) on Non-sequential LUN's are not registered with the OS. This happens across various HBA models and kernel versions. FYI, I'm currently running the latest qlogic qla2xxx drivers (8.02.14.01) against kernel 2.6.18-128.1.10.el5 x86_64 For example if the LUN mask is set to 0,1,2,3 then all is OK and all disks are configured. However, a mask of LUN 0 & 9 will not see the disks on LUN 9. It appears the kernel stops scanning when there is a gap in the LUN list. I read in a number of places how to fix this issue, and indeed here: http://filedownloads.qlogic.com/files/driver/48437/README_qla2xxx2-6U4.htm#BlacklistEntries Apparently, I should be able to add a line to modprobe.conf that allows sparse LUNs. So I followed the instructions and added options scsi_mod dev_flags="SUN:CSM200_R:0x040" max_luns=20 and rebuilt initrd. This doesn't seem to work, as only LUN 0 is configured by the OS despite LUN 9 also being unmasked. I've also tried options scsi_mod default_dev_flags=0x040 max_luns=20 in modprobe.conf with no luck [root at host qlogic]# cat /proc/scsi/qla2xxx/1 <snip> SCSI LUN Information: (Id:Lun) * - indicates lun is not registered with the OS. ( 0: 0): Total reqs 144, Pending reqs 0, flags 0x2, Dflags 0x0, 0:0:83 00 ( 0: 9): Total reqs 0, Pending reqs 0, flags 0x0*, Dflags 0x0, 0:0:83 00 [root at sgulfs-data1 ~]# cat /proc/scsi/scsi Attached devices: <snip> Host: scsi1 Channel: 00 Id: 00 Lun: 00 Vendor: SUN Model: CSM200_R Rev: 0616 Type: Direct-Access ANSI SCSI revision: 03 I can however do echo "scsi add-single-device 1 0 0 9" > /proc/scsi/scsi to enable LUN 9 and the disk is then configured. I've ended up writing a script in rc.local to enable the LUN , scan LVM and mount the file system which is not ideal. Does anyone have any further insight into how I could get the OS to enable these LUN's on boot thus eliminating the need for my doubtless dirty script? Cheers Dan