Saturday, February 20, 2010

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.

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