topic Re: Issue with LVM Disk and Help in Creating Disk in Operating System - HP-UX

Issue with LVM Disk and Help in Creating Disk

Jon Le — Wed, 30 Jul 2008 15:33:04 GMT

Hello everyone. Here are some details beforehand.

ioscan:
I have a HP-UX 9000, class RP5430.

the following scan is for a DS2100 external disk enclosure that has 3 harddrive in place.

0/3/0/0.0.0
sdisk claimed device seagate ST318404LC
/dev/dsk/c7t0d0
/dev/rdsk/c7t0d0

0/3/0/0.2.0
sdisk claimed device HP 18.2GST318406LC
/dev/dsk/c7t2d0
/dev/rdsk/c7t2d0

0/3/0/0.4.0
sdisk claimed device HP 18.2GST318406LC
/dev/dsk/c7t4d0
/dev/rdsk/c7t4d0

I had a disk go bad or a configuration error but I was using c7t0d0. However that disk got replaced and I want to use c7t0d0.

When I go into SAM in Disk Devices, it shows all 3 "unused".

Here is what I am trying to do. Begin to use all 3 disk. Each of the disk is 18.2 gig so I would like to have a volume group of 54.6 gig and possibly add more at a later date.

Here is the problem that I am running into:

when I do the following, i get the this error:

# pvdisplay /dev/dsk/c7t0d0
pvdisplay: Warning: couldn't query physical volume "/dev/dsk/c7t0d0": This specified path does not correspond to physical volume attached to this volume group
pvdisplay: warning: couldn't query all of the physical volumes.
pvdisplay; couldn't retrieve the names of the physical volumes belonging to volume group "/dev/test"
pvdisplay: cannot display physical volume "/dev/dsk/c7t0d0"

#vgdisplay /dev/test
vgdisplay: volume group not activated
vgdisplay: cannot display volume group "/dev/test"

#lvdisplay /dev/test/lvol1
lvdisplay: couldn't query logical volume "/dev/test/lvol1"
volume group not activated.

How do I go about resolving this error??

Also if you can provide me with a step by step instruction on how to start using the 3 disk. I know the steps involved but would like to confirm it with you guys. Thank you for your help in this matter.

Re: Issue with LVM Disk and Help in Creating Disk

James R. Ferguson — Wed, 30 Jul 2008 15:40:49 GMT

Hi Jon:

> vgdisplay /dev/test
> vgdisplay: volume group not activated

This means that the volume group is not active, so do:

# vgchange -a y /dev/test

Regards!

...JRF...

Re: Issue with LVM Disk and Help in Creating Disk

Jon Le — Wed, 30 Jul 2008 15:45:18 GMT

tried to activate it however here is what i am getting:

# vgchange -a y /dev/test

vgchange: warning: couldn't attach to the volume group physical volume "/dev/dsk/c7t0d0":
Cross device link
vgchange: warning: couldn't query physical volume "/dev/dsk/c7t0d0":
the specified path does not correspond to physical volume attached to this volume group
vgchange: warning: couldn't query all of the physical volume.
vgchange: couldn't activate volume group "/dev/test"
Quorum not present, or some physical volume(s) are missing.

Thank you for the quick response.

Re: Issue with LVM Disk and Help in Creating Disk

melvyn burnard — Wed, 30 Jul 2008 16:10:13 GMT

well if your disk has been replaced, you need to recreate the LVM headers on it.
Firstly though, do a strings /etc/lvmatb and verify what disks are in vg named test

If all three disks are listed, you can use vgcfgrestore to recreate the headers from the backupfile
man vgcfgrestore.

Re: Issue with LVM Disk and Help in Creating Disk

Jon Le — Wed, 30 Jul 2008 16:17:31 GMT

when I do a strings /etc/lvmtab

i get the following:

# strings /etc/lvmtab

/dev/vg01
/dev/dsk/c1t0d0
/dev/dsk/c2t0d0
/dev/dsk/c2t2d0
/dev/vg00
/dev/dsk/c1t2d0
/dev/test
/dev/dsk/c7t0d0

This is what is in my fstab file:

/dev/vg00/lvol3 / vxfs delaylog 0 1
/dev/vg00/lvol1 /stand hfs delaylog 0 1
/dev/vg00/lvol4 /tmp vxfs delaylog 0 2
/dev/vg00/lvol5 /home vxfs delaylog 0 2
/dev/vg00/lvol6 /opt vxfs delaylog 0 2
/dev/vg00/lvol7 /usr vxfs delaylog 0 2
/dev/vg00/lvol8 /var vxfs delaylog 0 2

/dev/vg01/data /data vxfs rw,suid,largefiles,delaylog,datainlog 0 2

/dev/test/lvol1 /test vxfs rw,suid,largefiles,delaylog,datainlog 0 2

Re: Issue with LVM Disk and Help in Creating Disk

Torsten. — Wed, 30 Jul 2008 16:52:56 GMT

The disk is still empty, but you have a valid VG backup for this disk.

# vgcfgrestore -n vgtest /dev/rdsk/c7t0d0

will restore the config.

# vgchange -a y vgtest

will activate the VG.

# vgdisplay -v vgtest

Now you need to do a "newfs" to the LVOLs (if there are any) to make them useable.

Re: Issue with LVM Disk and Help in Creating Disk

Jon Le — Wed, 30 Jul 2008 16:56:59 GMT

how do I start from scratch. Delete everything and begin from nothing.

Re: Issue with LVM Disk and Help in Creating Disk

Torsten. — Wed, 30 Jul 2008 16:59:10 GMT

You need to vgexport the vgtest in order to remove it from /etc/lvmtab.

man vgexport

Re: Issue with LVM Disk and Help in Creating Disk

Jon Le — Wed, 30 Jul 2008 17:09:29 GMT

thank you, i would run the following:

# vgexport -v -f backup /dev/test

after I do that, I can start with

1. creating a PV (pvcreate)
2. vgcreate
3. lvcreate

Re: Issue with LVM Disk and Help in Creating Disk

Tim Nelson — Wed, 30 Jul 2008 17:10:25 GMT

Here is what I would do after a bad disk replacement ( you can vgexport as mentioned because the data is gone any way) but this is good practice.

Remove old drive, insert new one.
ioscan
ioscan -kfnC disk ( look for your c7t0d0 disk as claimed)

vgcfgrestore -l -n /dev/vgtest ( this lists what devices the vgtest thinks it has)
vgcfgrestore -n /dev/vgtest /dev/rdsk/c7t0d0
vgchange -a y /dev/vgtest
vgdisplay -v /dev/vgtest

( In this case because you only had one drive and it is replaced, data is gone so.. )

newfs /dev/vgtest/rlvol1
mount /test-filesystem

or just start over

vgexport /dev/vgtest
pvcreate /dev/rdsk/c7t0d0
mkdir /dev/vgtest
mknod /dev/vgtest/group c 64 0x0Y0000 (pick a unique minor number for Y )
vgcreate /dev/vgtest /dev/dsk/c7t0d0
lvcreate -L SIZE_MB -n NAME /dev/vgtest
newfs /dev/vgtest/rNAME
edit /etc/fstab
mount /new_test_filesstem

Re: Issue with LVM Disk and Help in Creating Disk

Jon Le — Wed, 30 Jul 2008 17:28:03 GMT

thank you very much for the quick response.

I did the vgexport and was successful.

If I wanted to use all 3 disk combined together. I would do the following: correct me if any.

# pvcreate /dev/rdsk/c7t0d0
# pvcreate /dev/rdsk/c7t2d0
# pvcreate /dev/rdsk/c7t4d0

# mkdir /dev/vgtest
# mknod /dev/vgtest/group c 64 0x020000

the vgcreate is the one that I am confused about. There are multiple PV.

Can you provide me with the rest of the command to utilize the full extent of the 3 disk. Thank you so much for everyone's help.

I do have the HP-UX CSA desk reference but would like to get your input.

Re: Issue with LVM Disk and Help in Creating Disk

Torsten. — Wed, 30 Jul 2008 17:33:23 GMT

Now it depends if you want to add a larger disk anytime in future and if you want to stripe the LVOLs across all disks or if you want to mirror 1 disk to another.

Re: Issue with LVM Disk and Help in Creating Disk

Jon Le — Wed, 30 Jul 2008 17:34:40 GMT

eventually i would like to mirror the disk. I have the mirror software but haven't had a chance to implement it yet.

Re: Issue with LVM Disk and Help in Creating Disk

Torsten. — Wed, 30 Jul 2008 17:37:03 GMT

Re: Issue with LVM Disk and Help in Creating Disk

James R. Ferguson — Wed, 30 Jul 2008 17:38:58 GMT

Hi Jon:

# vgcreate /dev/vgtest /dev/dsk/c7t0d0 /dev/dsk/c7t2d0 /dev/dsk/c7t4d0

...will create a volume group (with defaults) containing the three physical disk provided as the arguments. The manpages for 'vgcreate' are your friend.

Regards!

...JRF...

Re: Issue with LVM Disk and Help in Creating Disk

Torsten. — Wed, 30 Jul 2008 17:47:56 GMT

I don't know how you want to use this VG in future ... but since a 73GB disk is the largest supported in this DS2100 I would extend the max_PE value to be able to include a 73GB disk later. Calculate the values depending on the PE_size you want to use.

Re: Issue with LVM Disk and Help in Creating Disk

Jon Le — Wed, 30 Jul 2008 17:48:07 GMT

If you mirror the question is: How about the third disk?

Depending on your hp-ux version you can either stripe **or** mirror the data.

Still the question is - would you like to add a larger disk in future?

BTW, are you running 11.11?

Well in the near future, I will be purchasing another DS that will have 4 drive in it so that I can mirror all the drives. Right now, there is not enough disk to mirror .

Currently there are 7 disk.

4 are internal disk having 18.2 gig each.
c1t0d0, c1t2d0, c2t0d0, c2t2d0.

/dev/vg01
/dev/dsk/c1t0d0
/dev/dsk/c2t0d0
/dev/dsk/c2t2d0
/dev/vg00
/dev/dsk/c1t2d0

those contain the boot and a majority of it is being used for storage of an application. I was going to use the DS2100 that I am configuring now to mirror those drive but I want to use it as an test environment.

On 2nd thought, I only really need to use one of the drive for this test environment. I don't need it to be mirrored as it is a test environment. Can I use the other 2 drive to mirror 2 of the internal drive? how do i go about doing that.

Re: Issue with LVM Disk and Help in Creating Disk

Michael Steele_2 — Wed, 30 Jul 2008 18:57:25 GMT

Hi:

Regarding "...Can I use the other 2 drive to mirror 2 of the internal drive? how do i go about doing that. ..."

You can do either. But there are some rules to follow when you mirror. You should use different controllers.

c0t0d0
c1t0d0

Here c0 and c1 are controllers. If you use c0 and c0 then you have a single point of failure (* SPOF *).

The targets should be the same. Although this may no longer be necessary in disk arrays, for SCSI JBODS its a must due to write scheduling priorities.

c0t0d0 and c1t0d0
not
c0t1do and c1t3do

Here t0, t1 and t3 are targets. The first example (* c0t0d0 and c1t0d0 *) are fine, the second is not.

Always use strict allocation policy. This is the default. This keeps you from mirroring extents back onto the primary. Like in your example of three disks. Eventually you will not be able to mirror additional logical volumes because of the strict allocation policy. In short, you want alternates to be identical to primaries (* mirrors *) and a three disk vg breaks this rule. One disk will not be mirrored.

Re: Issue with LVM Disk and Help in Creating Disk

Jon Le — Thu, 31 Jul 2008 15:34:56 GMT

thank you. What if I get a 72 gb drive for the ds2100 to occupy the last opening.

Right now on the ds2100 there are 4 slots. 3 of which is being used by 18.2 gig drives. If I get a 72 gb drive for the 4th slot. Can I use that 72 gb to mirror the 4 internal drive?

Here is my configuration:

HP9000 (internal drives):
c1t0d0
c1t2d0
c2t0do
c2t2d0

DS2100:
c7t0d0
c7t2d0
c7t4d0

Here is the VG and LV for HP9000:

c1t0d0, c2t0d0, c2t2d0 = vg01
with only one LV name of "storage"
storage - /storage - 52080 MB

c1t2d0 = vg00
with 8 LV.
vol1 - /stand - 300 MB
vol2 - /swap - 3072 MB
vol3 - / - 200 MB
vol4 - /tmp - 200 MB
vol5 - /home - 20 MB
vol6 - /opt - 664 MB
vol7 - /usr - 1104 MB
vol8 - /var - 3572 MB

So total of 9132 MB of c1t2d0.

What is your recommendation?

Re: Issue with LVM Disk and Help in Creating Disk

Michael Steele_2 — Thu, 31 Jul 2008 16:36:41 GMT

This may or may not work. You never get the full 72 GB. LVM will always subtract something for itself. For example, the VGRA header.

You also run into another rule. Any vg with a 73 GB disk will have to be the first disk added into the vg. If you add a 18 GB disk in first, and then vgextend in the 73 GB disk, then you'll only see the first 18 GB on this 73 GB disk.

Its worth a try but I think you'll end up with 2 complete mirrors and a 3rd mirror missing the last lvol.