vgcreate issue

[Norman_21]

Hello experts,

I've been having problems creating a new volume group in the same disk I have installed in my HP-UX workstation B180L.I have a single disk with 56MB available space.

#mkdir /dev/vg01
#mknod group c 64 0x010000
# vgcreate /dev/vg01 /dev/dsk/c0t6d0
Increased the number of physical extents per physical volume to 1023.
vgcreate: The physical volume "/dev/dsk/c0t6d0" is already recorded in the "/etc/lvmtab" file

I tried the following:
#pvcreate -f ....
#mv /etc/lvmtab /etc/lvmtab.old
#vgscan -v " returns the same error"
#strings /etc/lvmtab
/dev/vg00
/dev/dsk/c0t6d0

I also rebooted in a single user mode but I'm getting the same thing. Any thoughts, ideas.
Points will be rewarded.

[Michael Tully]

Hi Latif,

Is this disk part of an existing volume group? i.e. vg00 ? If so you can't create another volume group with the same disk.

Is this a second disk that was installed from another server?

Regards
Michael

[Norman_21]

Hey Mikey,

Glad to talk to you again. It's been a while.
Yes, this disk has vg00 on it. I guess I thought I can create a second VG in a single disk.

Any advice on a good cook book.
Thanks Micheale
LATIF

[Bill Hassell · Accepted solution]

A volume group has a minimum of 1 unused disk. Note that the use of pvcreate -f is very dangerous as it initializes the volume group information even though the disk might contain valid information. pv commands deal with physical disks (not parts of disks), as do vg commands. If you have extra space on vg00, you would use lvcreate to add a new logical volume. lv commands deal with portions of disk(s).

As far as documentation, all the HP-UX manuals are online and downloadable from: http://docs.hp.com but trying to learn concepts from reference manuals is like trying to learn English by reading a dictionary. I would start with "Disk and File Management Tasks on HP-UX" by Tom Madell (a bit dated: 1997) or get one of the Marty Poniatowski books such as "Learning the HP-UX Operating System" or "HP-UX 11.x System Administration How To Book". If you are using the obsolete 10.20 version of HP-UX, there is a 10.20 How To book with a used price of about $5.

[Michael Tully]

Latif,

Check out this document

http://docs.hp.com/hpux/onlinedocs/B2355-90742/B2355-90742.html

Regards
Michael

[twang]

I think that you cannot create a second VG in a single disk. LVM provides a way to combine one or more disks into a pool of available space(volume group), that pool can be subdivided into customized logical volumes to hold database, filesystems, swap space...
there are 4 principal objects to be dealt with when working with LVM, disk(physical volumes - disks are converted to PV through pvcreate), volume groups pool the PV into a large virtual space from which the rhird object, logical volumes, are allocated. VG are created and assigned a number of disks with vgcreate.

[Norman_21]

Hi guys,

Sorry for the delay. My HP-UX OS is 11.0

Very good info I'm using the HP-UX certified book but to be honest, this book is dedicated to prepare for the Exam but it's not good for daily system administration tasks. Therefore it was not clear to me weither to create multiple VGs in a single disk. However, I'll get online and find the books Bill advised and will read the document provided by Micheale.
Off course, thanks to Twang as well.

Once again.
Thanks to you all.

[Norman_21]

One more thing came to my attention.
How about when installing the HP-UX OS and then you chose the LVM ? I noticed that the help text states that LVM during the installation means if you have more 10 disk? DId I understand it correctly.
Please more explanation. I'm doing my HP-UX CSA and I need more info as much as I can get.

Thanks again.
Points will be rewarded at the end of this thread.

[twang]

Looking for infomation for HP-UX System Administration exam, you may share a moment of time to take a look at this thread:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x8e662d88ce9cd711abdc0090277a778c,00.html
good luck!
twang

[Bill Hassell]

LVM should be used for one disk or multiple disks. There is an option for an archaic design called whole-disk volumes, but there are so many upgrade and Ignite/UX issues that it is never recommended. Putting your system into whole-disk mode will make it very difficult for others to help you with problems. As far as 10 disks, the default limit for vgcreate is 16 (from the man page) but that can be overridden on the command line. The only limit of 10 I can think of is the default number of volume groups which is 10. This means that if you had hundreds of disks and wanted to create 20 separate volume groups, vgcreate would fail with the 11th VG.

Again, a volume group has a minimum of 1 physical disk, but may contain dozens. The idea is to collect space on one of more disks and then carve them up into the needed lvols.

[Norman_21]

Thanks Bill for your respond. However, I've been doing installations using the vxfs and not the LVM. I've not been having problems with installation and bringing up the HP-UX box. With the LVM option during the installation the file systems will not be created which means that will be a big work and complicated stuff so I would stick with the vxfs mode.

Twang,
Thanks for the Exam thread, I've been reading all the threads under Training and Education section and I went thru your thread before. I'll try to compromise all my Exam experience and post it as a guide line after passing the Exam.

Thanks again.

[Norman_21]

Thread closed