I'm testing LVM configurations for the purpose of building a home NAS with Ubuntu Server 16.04 LTS.
I first added three 20GB disks to my machine (sdb, sdc, sdd), created three physical volumes grouped in one volume group and finally created a RAID5 logical volume that spans across the three physical volumes. I used the following commands:

sudo pvcreate /dev/sdb /dev/sdc /dev/sdd
sudo vgcreate data /dev/sdb /dev/sdc /dev/sdd
sudo lvcreate --type raid5 --stripes 2 --size 15G --name test1 data

Then I added a fourth 20GB disk (sde), created a physical volume on it and added it to the data volume group:

sudo pvcreate /dev/sde
sudo vgextend data /dev/sde

How do I force the existing test1 logical volume to span across the four physical volumes and not only the first three?


Presumably this would do the trick:

sudo lvconvert --type raid5 --stripes 3 data/test1
  • Thanks for your answer. I get the following message when running the command: Using default stripesize 64.00 KiB. Converting the segment type for data/test1 from raid5 to raid5 is not yet supported. – Christophe May 4 '17 at 16:07
  • I also tried with a recent version of LVM, same issue. I guess I will go for a mdadm RAID5 instead. – Christophe May 5 '17 at 9:07
  • Yes, I hadn’t tried, but that “conversion” isn’t supported :-(. I get the impression you can only increase RAID levels but that’s just my first impression... It might be possible to switch to linear and back. – Stephen Kitt May 5 '17 at 9:34

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