LVM , RAID and new disks

Ammad · 01-09-2009, 11:23 AM

HI,

i installed RHEL5, with RAID + LVM on 2 disks, it was running fine with /dev/sda and /dev/sdb.
Today i added two new disks in system. after adding the previous disks changed to

Code:

/dev/sda --->  /dev/sdc
/dev/sdb --->  /dev/sdd

and New disks named 
/dev/sda
/dev/sdb

I can boot my system its working fine, but i cant create RAID on new disks, while booting system it displays an error/worning in LVM

Code:

 Incorrect metadata area header checksum

when i create a new RAID there is an error

Code:

root# mdadm --create --verbose /dev/md5 --level=1 --raid-devices=2 /dev/sda2 /dev/sdb2
mdadm: error opening /dev/md5: No such file or directory

IMP* SELINUX is disabled.

i dont have /dev/md5 , it should create new /dev/md5.

Any idea to solve this

thanks.

mostlyharmless · 01-09-2009, 12:49 PM

Well, clearly the message

Quote:

Incorrect metadata area header checksum

is because your new disks are being mistaken by the system for the old disks. It would have been better, perhaps, if you installed the new disks as /dev/sdc and /dev/sdd; changing the order in the BIOS might be possible.

As far as the second problem is concerned, you need to make the device /dev/md5 with mknod prior to creating the array with mdadm.

Ammad · 01-09-2009, 11:26 PM

thanks, i thought about that to change order but the system is IBM-P

, so have to change physical disks, so a new question

i am using Soft-raid, so if i replace both OS disks (RAID 1) to BAY 0,1. will it works without any lost of information (without failure of RAID).

for the RAID? when i first create /dev/md0-4 i didn't created node, then why now?

Thanks for your precious time .

mostlyharmless · 01-10-2009, 11:00 AM

Quote:

i am using Soft-raid, so if i replace both OS disks (RAID 1) to BAY 0,1. will it works without any lost of information (without failure of RAID).

Might work, and should be safe. Just be careful when you physically move the disks (antistatic precautions) and be careful before you write anything that you know what it is you are doing.. Bachups are always a must in this situation anyway.

Quote:

for the RAID? when i first create /dev/md0-4 i didn't created node, then why now?

Depending of the distro, there are a default number of md devices made, presumably 4 in your case.