分类： LINUX
2009-08-16 17:24:57
How to Create LV in Specifying Ranges
23:59 08/15/2009
Author: Jaylin Zhou
Test Environment:
RedHat Enterprise Linux 5.3
Symptom:
The allocation of LV is different from what is expected.
Solution:
Now there are two PVs:
# pvscan
PV /dev/sdb5 VG myvg lvm2 [192.00 MB / 192.00 MB free]
PV /dev/sdb6 VG myvg lvm2 [192.00 MB / 192.00 MB free]
Total: 2 [384.00 MB] / in use: 2 [384.00 MB] / in no VG: 0 [0 ]
Each of them has 48 PEs, and every PE is 4M.
A VG named "myvg" consists of sdb5 and sdb6
Now create LVs with
Example One:
Create a LV of 50 PEs specifying sdb5:0- and sdb6:0-
# lvcreate -l 50 /dev/myvg -n mylv /dev/sdb5:0- /dev/sdb6:0-
Logical volume "mylv" created
Example Two:
Create a LV of 50 PEs specifying sdb5:0-10 and sdb6:0-45
# lvcreate -l 50 /dev/myvg -n mylv /dev/sdb5:0-10 /dev/sdb6:0-45
Logical volume "mylv" created
Example Three:
Create a LV of 40 PEs specifying sdb5:0-40 and sdb6:0-20
# lvcreate -l 40 /dev/myvg -n mylv /dev/sdb5:0-40 /dev/sdb6:0-20
Logical volume "mylv" created
Example Four:
Create a LV of 40 PEs specifying sdb5:0-20 and sdb6:0-40
# lvcreate -l 40 /dev/myvg -n mylv /dev/sdb5:0-20 /dev/sdb6:0-40
Logical volume "mylv" created
Example Five:
Create a LV of 20 PEs specifying sdb5:0-30 and sdb6:0-40
# lvcreate -l 40 /dev/myvg -n mylv /dev/sdb5:0-30 /dev/sdb6:0-40
Logical volume "mylv" created
Example Six:
Create a LV of 20 PEs specifying sdb5:0-30 and sdb6:0-29
# lvcreate -l 40 /dev/myvg -n mylv /dev/sdb5:0-30 /dev/sdb6:0-29
Logical volume "mylv" created
Example Seven:
Create a LV of 20 PEs specifying sdb5:0-30 and sdb6:0-30
# lvcreate -l 20 /dev/myvg -n mylv /dev/sdb5:0-30 /dev/sdb6:0-30
Logical volume "mylv" created
Example Eight:
Create a LV of 60 PEs without specifying PVs
# lvcreate -l 60 /dev/myvg -n mylv
Logical volume "mylv" created
Summary:
From the experiments above, there are some rules of how to create an LV by specifying PV ranges:
Rule One: OS gives the priority to the PV of bigger range.
Rule Two: If without specifying the range, OS gives the priority to the former one.
Rule Three: If the two ranges are equal, OS gives the priority to the former one.
