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I'm trying to create a RAID5 software array using LVM. I use VirtualBox as I'm only learning how LVM works. So I've created 4 virtual SCSI drives and then did the following:

pvcreate /dev/sd[b-e]
vgcreate /dev/sd[b-e] raid5_vg
lvcreate --type raid5 -i 3 -L 1G -n raid_lv raid5_vg

However, I get an error after the last command:

WARNING: Unrecognised segment type raid5
Using default stripesize 64.00 KiB
Rounding size (256 extents) up to stripe boundary size (258 extents)
Cannot update volume group raid5_vg with unknown segments in it!

So it looks like raid5 is not a valid segment type. "lvm segtypes" also doesn't contain 'raid5' entry:

root@ubuntu-lvm:~# lvm segtypes
  striped
  zero
  error
  free
  snapshot
  mirror

So my question is - how could I create RAID5 logical volume using LVM only? It seems that it is possible, I saw a few references (not for Ubuntu, unfortunately) for RedHat and Gentoo systems. I don't want to use mdadm for now, until I find out that it is mandatory.

Some info about my system is below:

root@ubuntu-lvm:~# uname -a
Linux ubuntu-lvm 3.8.0I use Ubuntu Server 12.04.3 (i686)-29-generic #42~precise1-Ubuntu SMP Wed Aug 14 15:31:16 UTC 2013 i686 i686 i386 GNU/Linux


root@ubuntu-lvm:~# dpkg -l | grep lvm
ii  lvm2                             2.02.66-4ubuntu7.3                The Linux Logical Volume Manager

Thanks.

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1 Answer 1

up vote 2 down vote accepted

LVM raid5 support is rather new and experimental. As such, it isn't supported in 12.04. The conventional thing to do is to use mdadm to create a raid array, then use lvm to carve that up into logical volumes.

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Thanks! So, I have to use mdadm. –  April Ethereal Oct 22 '13 at 20:30

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