LVM mirror creation problem

UNIX for Advanced & Expert Users
1

I apologize is this isn't an appropriate post for the 'advanced' UNIX, so please let me know if I should post this under UNIX for dummies, but here's my problem in a nutshell: I having problems creating a mirrored logical volume.

I have created two new physical volumes

root@ubuntu:/home/ubuntu# pvcreate /dev/sdc1 /dev/sdd1
  Physical volume "/dev/sdc1" successfully created
  Physical volume "/dev/sdd1" successfully created

I have created a volume group:

root@ubuntu:/home/ubuntu# vgcreate RAID1 /dev/sdc1 /dev/sdd1
  Volume group "RAID1" successfully created

root@ubuntu:/home/ubuntu# vgdisplay RAID1
  --- Volume group ---
  VG Name               RAID1
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  1
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               3.06 TiB
  PE Size               4.00 MiB
  Total PE              801288
  Alloc PE / Size       0 / 0   
  Free  PE / Size       801288 / 3.06 TiB
  VG UUID               ICsqOA-MMmL-wuOA-PqqA-oJ1o-vIeU-sG89xA

So far so good. I seem to have 3TB of free space to use.

I can create a striped volume

root@ubuntu:/home/ubuntu# lvcreate -i2 -l30%FREE -n test -I 128 RAID1 
  Logical volume "test" created
root@ubuntu:/home/ubuntu# lvchange -an RAID1/test
root@ubuntu:/home/ubuntu# lvremove RAID1/test

However when I try to create a mirrored volume, I get this:

root@ubuntu:/home/ubuntu# lvcreate -n backup -m1 --mirrorlog mirrored -l 30%VG RAID1
  Not enough PVs with free space available for parallel allocation.
  Consider --alloc anywhere if desperate.
  Unable to allocate extents for mirror(s).

Very puzzling. Can anyone tell me what I'm doign wrong?

Many thanks

---------- Post updated at 02:37 PM ---------- Previous update was at 12:40 PM ----------

Problem solved - user error. I didn't give the vg 2 additional volumes needed for the disk log

2

Thank you for following up with your solution. It may help someone else.

Regards and welcome to the forum,
Alister

3

To elaborate a little on my rather terse "solution", as I understand it, lvcreate uses the last physical disks (if specified) as the location of the disk logs.

So if you don't specify --mirrorlog core you will need at least three physical volumes, two for the data and one (which is on a separate PV) for the disk log. In this case, the last extent specified is where the log will be stored.

If you use --mirrorlog mirrored, you will need two physical devices for the two logs, and lvcreate will take the last two PV as the location of the logs.