Saturday, February 20, 2010

Grub woes with my 2 TB disk

This is my first time using a 2 TB disk. After performing a Ubuntu Karmic Update on it, it upgraded the kernel and it asked "Configure GRUB using the package maintainers version". What made me do this I don't know, but I think this totally messed me up. It seemed like it deleted the bios partition.

When the disk booted, it printed the following on the screen and then just hung


The fix for this whole mess, I loaded the Ubuntu bootup USB stick, and recreated the BIOS disk partition. After doing this, I executed /usr/sbin/grub-install /dev/sda, then everything started working.

LVM2 error: Cannot add 16th partition using pvcreate

Got a 2TB disk that has 48 raw partitions that I want to add to LVM.
When creating the partitions, I thought it wouldn't let me do more then 16 partitions. I was delighted to know that I could go beyond this 16 partition limitation. I guess maybe with new disks this is not a problem?? Don't know why.

Go this error message when I was in the process of upgrading my hard disk.

#sudo pvcreate /dev/sdc16
Device /dev/sdc16 not found (or ignored by filtering).

I reran the command with the "-vvv" option. It failed because of the following error message

/dev/sdc16: Skipping: Unrecognised LVM device type 259

After much web searching I found that this type is known as blkext

So I added the following line to lvm.conf

types = ['blkext', 50]

After doing this, I can now add all the remaining 40+ partitions to LVM.

This setup is for my mythtv production box. I use the same PC as a backend and frontend. Its not advisable I think but I have to do it this way. I use a Logical volume to store recordings. I found that my performance is greatly improved if the physical partitions are small. My thought is that this reduces seek time. I saw improvements after doing this when my PC is taping 2 HD shows and I'm watching a HD show at the same time. Maybe my theory may be wrong, but this works for me.