Redhat
Linux’s Logical volume Manager has many attributes which are available
for controlling the behavior LVM objects or to changing the default
values of LVM. We may not use those attributes very often in typical
production environment but knowing is not a bad thing. As a Unix/Linux
admin,we should have capability to explain each and every field of
commands output as most of the fields will reflect the attributes
value.Here we will see some of LVM attributes.
Physical volume(PV) attributes:
To check the physical volume attributes,use “pvs” command.The forth column of pvs command output displays the physical volume attributes.[root@mylinz ~]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 /dev/sdd1 uavg lvm2 a- 508.00m 408.00m /dev/sde uavg lvm2 a- 508.00m 508.00m /dev/sdf uavg lvm2 a- 5.00g 5.00g [root@mylinz ~]#The above command output shows “a” in the attribute field which explains that physical volumes can be “allocated” to the volumes.
Export the volume group “uavg” and check pvs output.
[root@mylinz ~]# vgexport uavg Volume group "uavg" successfully exported [root@mylinz ~]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 /dev/sdd1 uavg lvm2 ax 508.00m 408.00m /dev/sde uavg lvm2 ax 508.00m 508.00m /dev/sdf uavg lvm2 ax 5.00g 5.00g [root@mylinz ~]#In attributes field, you can see that “x” is added now.This show that volume group is exported.
We can stop the allocation to the disk by using pvchnage command.By disabling allocation,volume will not be extended using that specific physical volume.
[root@mylinz ~]# pvchange -x n /dev/sdd1 Physical volume "/dev/sdd1" changed 1 physical volume changed / 0 physical volumes not changed [root@mylinz ~]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 /dev/sdd1 uavg lvm2 -- 508.00m 408.00m /dev/sde uavg lvm2 a- 508.00m 508.00m /dev/sdf uavg lvm2 a- 5.00g 5.00g [root@mylinz ~]#You can revert the change any time using below mentioned command.
[root@mylinz ~]# pvchange -x y /dev/sdd1 Physical volume "/dev/sdd1" changed 1 physical volume changed / 0 physical volumes not changed [root@mylinz ~]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 /dev/sdd1 uavg lvm2 a- 508.00m 408.00m /dev/sde uavg lvm2 a- 508.00m 508.00m /dev/sdf uavg lvm2 a- 5.00g 5.00g [root@mylinz ~]#Some of the useful commands to get the details of physical volume.
1.To get the physical volumes with “UID” , use “-v” option.
Note:You can also use “pvs -vv” to get more detailed information.
[root@mylinz ~]# pvs -v Scanning for physical volume names PV VG Fmt Attr PSize PFree DevSize PV UUID /dev/sdd1 uavg lvm2 ax 508.00m 408.00m 511.98m tJ5YhP-VOZV-yfQ6-Uyye-WGT7-VLcl-7M3RMK /dev/sde uavg lvm2 ax 508.00m 508.00m 512.00m FadWLT-LjD8-v8VB-pboY-eZbK-vYpE-ZWq0i9 /dev/sdf uavg lvm2 ax 5.00g 5.00g 5.00g GbvgWh-l0w3-wCA6-umkD-zfsS-8yAZ-GeOSKF [root@mylinz ~]#
2.To get all the disks connected to the system ,use “pvs -a”
[root@mylinz ~]# pvs -a PV VG Fmt Attr PSize PFree /dev/root -- 0 0 /dev/sda1 -- 0 0 /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 /dev/sdb1 -- 0 0 /dev/sdc1 -- 0 0 /dev/sdd1 uavg lvm2 ax 508.00m 408.00m /dev/sde uavg lvm2 ax 508.00m 508.00m /dev/sdf uavg lvm2 ax 5.00g 5.00g /dev/sdg -- 0 0 /dev/vg_mylinz/lv_swap -- 0 0 [root@mylinz ~]#/dev/sda1 is not part of LVM but you get the disk list in pvs command.
3.To get the segment wise output,use below command.
[root@mylinz ~]# pvs --segments PV VG Fmt Attr PSize PFree Start SSize /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 0 4234 /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 4234 760 /dev/sdd1 uavg lvm2 ax 508.00m 408.00m 0 13 /dev/sdd1 uavg lvm2 ax 508.00m 408.00m 13 25 /dev/sdd1 uavg lvm2 ax 508.00m 408.00m 38 89 /dev/sde uavg lvm2 ax 508.00m 508.00m 0 127 /dev/sdf uavg lvm2 ax 5.00g 5.00g 0 1279 [root@mylinz ~]#
Volume Group(VG) Attributes:
You can see the volume group attributes using vgs command.
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Here we will see sample vgs command output.
There are some other volume group attributes which will be useful while creating the new volume group.
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background-color: #104E8B; color: #FFF; font-weight: bold; }table.tableizer-table { border: 1px solid #CCC; font-family: Arial, Helvetica, sans-serif font-size: 12px; } .tableizer-table td { padding: 4px; margin: 3px; border: 1px solid #ccc; } .tableizer-table th { background-color: #104E8B; color: #FFF; font-weight: bold; }
| Attributes | Description |
|---|---|
| r,w | (r)ead & (w)rite permissions |
| z | resi(z)eable |
| x | e(x)ported |
| p | (p)artial |
| c,n,a,i | allocation policy (c)ontiguous, c(l)ing, (n)ormal, (a)nywhere, (i)nherited |
| c | (c)luster |
[root@mylinz ~]# vgs
VG #PV #LV #SN Attr VSize VFree
uavg 3 1 0 wz--n- 5.99g 5.89g
vg_mylinz 1 2 0 wz--n- 19.51g 0
[root@mylinz ~]#
[root@mylinz ~]# vgs -v
Finding all volume groups
Finding volume group "uavg"
Finding volume group "vg_mylinz"
VG Attr Ext #PV #LV #SN VSize VFree VG UUID
uavg wz--n- 4.00m 3 1 0 5.99g 5.89g c87FyZ-5DND-oQ3n-iTh1-Vb1f-nBML-vUBUE9
vg_mylinz wz--n- 4.00m 1 2 0 19.51g 0 dIgmLP-aoe3-anxY-WHYE-bBtX-u28M-WF6Ye5
[root@mylinz ~]#
There are some other volume group attributes which will be useful while creating the new volume group.
| Attributes | Description |
|---|---|
| -l | maximum logical volumes |
| -p | maximum physical volumes |
| -s | physical extent size (default is 4MB) |
| -A | autobackup |
All the above
mentioned attributes can be set while creating the volume group.You can
not modify those values after that.In the below example,I have used most
the attributes with specific value to create new volume group.
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background-color: #104E8B; color: #FFF; font-weight: bold; }[root@mylinz ~]# vgcreate -l 512 -p 256 -s 32M -Ay newvg /dev/sdf Volume group "newvg" successfully created vgs newvg VG #PV #LV #SN Attr VSize VFree newvg 1 0 0 wz--n- 4.97g 4.97g [root@mylinz ~]#You can see the newly set values in vgdisplay command output.
[root@mylinz ~]# vgdisplay -v newvg
Using volume group(s) on command line
Finding volume group "newvg"
--- Volume group ---
VG Name newvg
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 512
Cur LV 0
Open LV 0
Max PV 256
Cur PV 1
Act PV 1
VG Size 4.97 GiB
PE Size 32.00 MiB
Total PE 159
Alloc PE / Size 0 / 0
Free PE / Size 159 / 4.97 GiB
VG UUID Ny4xsv-uJ49-sZr9-lvfq-Oa7n-l5mH-1bPBbp
--- Physical volumes ---
PV Name /dev/sdf
PV UUID GbvgWh-l0w3-wCA6-umkD-zfsS-8yAZ-GeOSKF
PV Status allocatable
Total PE / Free PE 159 / 159
[root@mylinz ~]#
Logical Volume (LV) Attributes:
Knowing the logical volume attributes.[root@mylinz ~]# lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert vol1 uavg -wi-ao 100.00m lv_root vg_mylinz -wi-ao 16.54g lv_swap vg_mylinz -wi-ao 2.97g [root@mylinz ~]#The below tables covers the “lvs” command attributes. table.tableizer-table { border: 1px solid #CCC; font-family: Arial, Helvetica, sans-serif font-size: 12px; } .tableizer-table td { padding: 4px; margin: 3px; border: 1px solid #ccc; } .tableizer-table th { background-color: #104E8B; color: #FFF; font-weight: bold; }
| Volume Type Attributes(First Field of Attr) | Description |
|---|---|
| m | (m)irrored |
| M | (M)irrored without intial sync |
| o | (o)rgin |
| p | (p)vmove |
| s | (s)napshot |
| S | invalid (S)napshot |
| v | (v)irtual |
| i | mirror (i)mage |
| l | mirror (I)mage without sync |
| c | under (c)onstruction |
| – | Simple Volume |
| Attributes (second to sixth Field of Attr) | Description |
|---|---|
| w,r (Second Feild) | Permissions ‘(r)’ead ‘(w)’rite |
| c,I,n.a,I (Third Feild) | Allocation policy (c)ontiguous, c(l)ing, (n)ormal, (a)nywhere, (i)nherited |
| m (Fourth Feild) | Fixed (m)inor |
| a,s,I (Fifth Feild) | (a)ctive, (s)uspended, (I)nvalid snapshot,, |
| S (Fifth Feild) | Invalid (S)uspended snapshot |
| I (Fifth Feild) | Mapped device present with (i)nactive table |
| d (Fifth Feild) | Mapped (d)evice present with-out tables |
| o (sixth Feild) | device (o)pen (Volume is in active state or may be mounted ) |
While creating the volume can provide various attributes like stripe size,no of extends
etc.These are already covered in volume creation.
Here we will see some of the useful “lvs” command options.
1.To display the logical volumes with underlying physical volumes use,
2.To see the complete physical disks segmnets for logical volumes,
3.For detailed logical volume information,
Hope this post is informative for you.Thank you for reading this article.Please leave a comment if you have any doubt.I will get back to you.
Here we will see some of the useful “lvs” command options.
1.To display the logical volumes with underlying physical volumes use,
[root@mylinz ~]# lvs -a -o +devices LV VG Attr LSize Origin Snap% Move Log Copy% Convert Devices vol1 uavg -wi-ao 100.00m /dev/sdd1(13) lv_root vg_mylinz -wi-ao 16.54g /dev/sda2(0) lv_swap vg_mylinz -wi-ao 2.97g /dev/sda2(4234) [root@mylinz ~]#
2.To see the complete physical disks segmnets for logical volumes,
[root@mylinz ~]# lvs -a -o +seg_pe_ranges --segments LV VG Attr #Str Type SSize PE Ranges vol1 uavg -wi-ao 1 linear 100.00m /dev/sdd1:13-37 lv_root vg_mylinz -wi-ao 1 linear 16.54g /dev/sda2:0-4233 lv_swap vg_mylinz -wi-ao 1 linear 2.97g /dev/sda2:4234-4993 [root@mylinz ~]#
3.For detailed logical volume information,
[root@mylinz ~]# lvdisplay --maps /dev/uavg/vol1
--- Logical volume ---
LV Name /dev/uavg/vol1
VG Name uavg
LV UUID XjMpRC-6f5k-FN9L-jz5v-f0Gj-wBpf-xc9GVD
LV Write Access read/write
LV Status available
# open 1
LV Size 100.00 MiB
Current LE 25
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:2
--- Segments ---
Logical extent 0 to 24:
Type linear
Physical volume /dev/sdd1
Physical extents 13 to 37
[root@mylinz ~]#
Hope this post is informative for you.Thank you for reading this article.Please leave a comment if you have any doubt.I will get back to you.
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