sdb instead of sda -> Help needed
Posted by CoolMike, 07-17-2007, 03:23 AM Hi I have a server with a raid5 configuration. Linux recognize it as sdb. But sda is not existing at all. Here is an output of fdisk -l: This would not be a problem. But I need to do a baremetal restore to this server and there it is required, that the disk is called sda. How can i change this? Michael
Posted by bornforlamp, 07-17-2007, 03:35 AM Hello, sda does not exists it may be attached as a secondary. so it is not displaying sda
Posted by CoolMike, 07-17-2007, 03:39 AM I'm just wondering, with IDE it was quite easy to say which disk is hda and which is hdb. But this is a hardware raid 5, with 4 SAS disks. How can I change it here that it is recognized as sda?
Posted by bornforlamp, 07-17-2007, 03:52 AM May be you have hardware raid configured and it is attached as a secondary, so it is displaying sdb instead of sda. You need to contact your Datacenter for changing it to sda
Posted by CoolMike, 07-17-2007, 04:04 AM I'm the owner of the hardware and need to go to the datacenter by my self. But how can i attach a hardware raid to primary? This is a raid controller with 4 cables which are going to the SAS disk. That's not the same like IDE with primary/secondary.
Posted by eztiger, 07-17-2007, 04:20 AM Check dmesg...do you have something else plugged in that is being picked up as a scsi device before your raid controller? (usb stick perhaps?). Also check /etc/modules.conf (or equivalent) and make sure nothing ni there is grabbing sda. Depending on distro you could also check your udev rules as well. I'd eliminate the possibility of something else using sda before you proceed. What changed to make it hop from sda -> sdb? Or am I missing something? Kev
Posted by CoolMike, 07-17-2007, 07:50 AM I found in dmesg the following line: There is no usb device conected and i have no idea what this could be. It was always like this, but i have to run a baremetal restore and I can only restore it, if the disk is under /dev/sda. Michael
Posted by eztiger, 07-17-2007, 08:02 AM Why does the bare metal restore require it to be /dev/sda? what are you using? My only suggestion is that : - *something* is being picked up as sda...find out what it is and remove it or remove it's kernel module (if possible) - add a udeb rule to try and force your sdb -> sda. i don't think this will work though. Kev
Posted by CoolMike, 07-17-2007, 08:08 AM I'm using the backup solution from r1soft.com. It requires, when you make a backup from sda, the baremetal restore also need to be on sdb. I have two identical servers and need to restore now to the second server.
Posted by CoolMike, 07-17-2007, 08:23 AM How can I add this udeb rule? Do you mean udev?
Posted by eztiger, 07-17-2007, 08:30 AM Sorry, yes - udev. I don't think you can override if theres already something on sda though. You could look at the scsi id's / luns for your array. See if you can shift it a bit. Might make the kernel find it before the other sda device. The key to it all is the unknown sda device. For future reference you could have a look at something like device mapper which will allow you to assign a 'logical' name to a scsi device. And then you reference that from there on in. It means you would avoid the problem you're seeing - where SCSI devices are detected in an undeterminant order. I've used it with SAN's with no problems - I would presume the same theory applies to locally attached disks - using lun ids instead of SAN WWID's LVM or possibly even ext disk labels might also help. The backup solution doesn't sound very flexible though Kev
Posted by eztiger, 07-17-2007, 08:32 AM If you have full remote kvm access to the server and don't know what the unknown sda device is I would go through the BIOS and disable everything you don't need. Hopefully this will remove what it is (i.e if usb is disabled then nothing plugged in will be detected etc). Plucking at straws now however. Kev
Posted by CoolMike, 07-17-2007, 09:07 AM That's bad, it's a usb keyboard, therefore i can not turn off the usb support in the bios. But would a usb device be recognized as scsi?
Posted by eztiger, 07-17-2007, 09:18 AM Surely you can turn it off for the purposes of doing your restore? you shouldn't need it if you're not at the machine? I also don't know why it would turn up as a block device to the kernel... Lots of funny things going on with your machine! I'd still be disabling usb.. Kev
Posted by CoolMike, 07-17-2007, 10:34 AM To do the baremetal restore I have to boot the server with a boot cd. Then i have to give a IP address and from this point on, i don't need the keyboard anymore. As you can see, this is not that easy... :-)
Posted by eztiger, 07-17-2007, 10:49 AM ps2 connectors on the board? no iLO? no other form of console / serial access? Not much more I can offer - but your setup sounds bizarre good luck whatever you choose to do! Kev