Hi, I am facing very weird issue on RHEL6 when SAN cable/Luns are attached. Below is the issue summary: 1. I have installed RHEL6 OS (when SAN cable was not attached to the system) with desktop option, system has 4 internal disks. a. While OS installation internal disks was showing as sdb, sdc, sdd and sde and I installed root, boot and swap on sdb b. After OS installation done which went up and running properly. But, now, my disk labeling changed to sda, sdb, sdc and sdd. (some commands I fired on that live server are below) [root@rh12 /]# df -h Filesystem Size Used Avail Use% Mounted on /dev/md1 29G 3.3G 25G 12% / tmpfs 499M 100K 499M 1% /dev/shm /dev/sda1 2.0G 68M 1.8G 4% /boot [root@rh12 /]# fdisk -l Disk /dev/sda: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xe008fd5e Device Boot Start End Blocks Id System /dev/sda1 * 1 256 2048000 83 Linux Partition 1 does not end on cylinder boundary. /dev/sda2 256 4080 30720000 fd Linux raid autodetect /dev/sda3 4080 4717 5120000 82 Linux swap / Solaris Disk /dev/sdb: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0006cc86 Device Boot Start End Blocks Id System /dev/sdb1 1 3825 30720000 fd Linux raid autodetect Disk /dev/sdc: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdc doesn't contain a valid partition table Disk /dev/sdd: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdd doesn't contain a valid partition table Disk /dev/md1: 31.5 GB, 31456157696 bytes 2 heads, 4 sectors/track, 7679726 cylinders Units = cylinders of 8 * 512 = 4096 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/md1 doesn't contain a valid partition table [root@rh12 /]# cat /proc/scsi/scsi Attached devices: Host: scsi4 Channel: 00 Id: 00 Lun: 00 Vendor: ATA Model: GB0160CAABV Rev: n/a Type: Direct-Access ANSI SCSI revision: 05 Host: scsi4 Channel: 00 Id: 01 Lun: 00 Vendor: ATA Model: GB0160CAABV Rev: n/a Type: Direct-Access ANSI SCSI revision: 05 Host: scsi5 Channel: 00 Id: 00 Lun: 00 Vendor: ATA Model: GB0160CAABV Rev: n/a Type: Direct-Access ANSI SCSI revision: 05 Host: scsi5 Channel: 00 Id: 01 Lun: 00 Vendor: ATA Model: GB0160CAABV Rev: n/a Type: Direct-Access ANSI SCSI revision: 05 Host: scsi6 Channel: 00 Id: 00 Lun: 00 Vendor: HL-DT-ST Model: DVDRAM GSA-E10L Rev: LE05 Type: CD-ROM ANSI SCSI revision: 00 Host: scsi7 Channel: 00 Id: 00 Lun: 00 Vendor: KVM Model: vmDisk-CD Rev: 0.01 Type: CD-ROM ANSI SCSI revision: 00 Host: scsi8 Channel: 00 Id: 00 Lun: 00 Vendor: KVM Model: vmDisk Rev: 0.01 Type: Direct-Access ANSI SCSI revision: 00 [root@rh12 /]# c. I rebooted the system several times but getting the same results.. no worries as system was working properly. No issues. 2. Now, I attached SAN cable and SAN luns to the system when system was live i.e. when it was up and running, then I fired some commands as below (After SAN cables+Luns attached to live system but before reboot) [root@rh12 ~]# cat /proc/scsi/scsi Attached devices: Host: scsi4 Channel: 00 Id: 00 Lun: 00 Vendor: ATA Model: GB0160CAABV Rev: n/a Type: Direct-Access ANSI SCSI revision: 05 Host: scsi4 Channel: 00 Id: 01 Lun: 00 Vendor: ATA Model: GB0160CAABV Rev: n/a Type: Direct-Access ANSI SCSI revision: 05 Host: scsi5 Channel: 00 Id: 00 Lun: 00 Vendor: ATA Model: GB0160CAABV Rev: n/a Type: Direct-Access ANSI SCSI revision: 05 Host: scsi5 Channel: 00 Id: 01 Lun: 00 Vendor: ATA Model: GB0160CAABV Rev: n/a Type: Direct-Access ANSI SCSI revision: 05 Host: scsi6 Channel: 00 Id: 00 Lun: 00 Vendor: HL-DT-ST Model: DVDRAM GSA-E10L Rev: LE05 Type: CD-ROM ANSI SCSI revision: 00 Host: scsi7 Channel: 00 Id: 00 Lun: 00 Vendor: KVM Model: vmDisk-CD Rev: 0.01 Type: CD-ROM ANSI SCSI revision: 00 Host: scsi8 Channel: 00 Id: 00 Lun: 00 Vendor: KVM Model: vmDisk Rev: 0.01 Type: Direct-Access ANSI SCSI revision: 00 Host: scsi0 Channel: 00 Id: 00 Lun: 00 Vendor: DGC Model: LUNZ Rev: 0219 Type: Direct-Access ANSI SCSI revision: 04 Host: scsi0 Channel: 00 Id: 01 Lun: 00 Vendor: DGC Model: RAID 5 Rev: 0220 Type: Direct-Access ANSI SCSI revision: 04 Host: scsi0 Channel: 00 Id: 01 Lun: 01 Vendor: DGC Model: RAID 5 Rev: 0220 Type: Direct-Access ANSI SCSI revision: 04 Host: scsi0 Channel: 00 Id: 01 Lun: 02 Vendor: DGC Model: RAID 5 Rev: 0220 Type: Direct-Access ANSI SCSI revision: 04 [root@rh12 ~]# [root@rh12 ~]# fdisk -l Disk /dev/sdc: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdc doesn't contain a valid partition table Disk /dev/sda: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xe008fd5e Device Boot Start End Blocks Id System /dev/sda1 * 1 256 2048000 83 Linux Partition 1 does not end on cylinder boundary. /dev/sda2 256 4080 30720000 fd Linux raid autodetect /dev/sda3 4080 4717 5120000 82 Linux swap / Solaris Disk /dev/sdb: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0006cc86 Device Boot Start End Blocks Id System /dev/sdb1 1 3825 30720000 fd Linux raid autodetect Disk /dev/sdd: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdd doesn't contain a valid partition table Disk /dev/md1: 31.5 GB, 31456157696 bytes 2 heads, 4 sectors/track, 7679726 cylinders Units = cylinders of 8 * 512 = 4096 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/md1 doesn't contain a valid partition table Disk /dev/sdg: 16.1 GB, 16106127360 bytes 64 heads, 32 sectors/track, 15360 cylinders Units = cylinders of 2048 * 512 = 1048576 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdg doesn't contain a valid partition table Disk /dev/sdh: 16.1 GB, 16106127360 bytes 64 heads, 32 sectors/track, 15360 cylinders Units = cylinders of 2048 * 512 = 1048576 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdh doesn't contain a valid partition table Disk /dev/sdi: 16.1 GB, 16106127360 bytes 64 heads, 32 sectors/track, 15360 cylinders Units = cylinders of 2048 * 512 = 1048576 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/sdi doesn't contain a valid partition table [root@rh12 ~]# cat /proc/partitions major minor #blocks name 8 32 156290904 sdc 8 0 156290904 sda 8 1 2048000 sda1 8 2 30720000 sda2 8 3 5120000 sda3 8 16 156290904 sdb 8 17 30720000 sdb1 8 48 156290904 sdd 9 1 30718904 md1 8 96 15728640 sdg 8 112 15728640 sdh 8 128 15728640 sdi [root@rh12 ~]# lsscsi [0:0:0:0] disk DGC LUNZ 0219 /dev/sdf [0:0:1:0] disk DGC RAID 5 0220 /dev/sdg [0:0:1:1] disk DGC RAID 5 0220 /dev/sdh [0:0:1:2] disk DGC RAID 5 0220 /dev/sdi [4:0:0:0] disk ATA GB0160CAABV n/a /dev/sda [4:0:1:0] disk ATA GB0160CAABV n/a /dev/sdb [5:0:0:0] disk ATA GB0160CAABV n/a /dev/sdc [5:0:1:0] disk ATA GB0160CAABV n/a /dev/sdd [6:0:0:0] cd/dvd HL-DT-ST DVDRAM GSA-E10L LE05 /dev/sr0 [7:0:0:0] cd/dvd KVM vmDisk-CD 0.01 /dev/sr1 [8:0:0:0] disk KVM vmDisk 0.01 /dev/sde 3. Then, I rebooted the system and for my surprise, it was not booting up and throwing error message “No root device found, Boot has failed, sleeping forever” a. Reason i guess is that, system tries to boot from SAN disk instead of internal disk and fails to boot b. I have checked in the BIOS setting that first boot priority is set to Internal disk and not SAN disk. 4. When I removed the SAN cable from the system, it again boots up properly. No issues found. Can anyone let me know the solutions for that and any reason why this is happening? Thanks in Advance!!!! Thanks, Amrish Parikh