Problems with new 18Gb disk

[Kevin Bingham]

Hi,
I have a 9000/803 D220 running HP-UX 11.0 (32 bit). I have just added a new disk (18Gb in size) to the machine. When I booted, the device was visible with correct size and Seagate model number via "ioscan" (/dev/dsk/c0t4d0, SCSI ID = 4) . So, I started SAM and added the new disk to the single non-mirrored VG (vg00) that we have. When I was adding space to my LV (/apps), I noticed freespace at approx 10Gb instead of 18.5Gb as expected. I had 0.5Gb free space before the new disk went in.

Since I have added space to the /apps, the new disk is "in use" even though I haven't written to /apps since starting this process.

I tried pvmove to get the extents off the new disk, but there is not enough space on the other disks to take the extents off the new disk. Not sure if lvreduce is applicable since there is no mirror-ing...

What can I do to get to see/use the other 8Gb of disk space?

Thanks in advance.
Kevin

[Stefan Farrelly]

I think youve hit a Volume group limit. My guess is your existing disk in the same volume group is 9GB, and youve added an 18GB disk to it. You cant do this an have the full 18GB available to use, you can only use the first 9GB of it as when your VG was created the max PE per PV value was set for a 9 GB drive, not 18 GB.

you need to recreate your VG. Best way to do this is use Ignite's make_recovery command (if VG00), boot from the tape and reinstall/rebuild VG00 using the 18GB drive. Long job im afraid.

If not VG00 then create a new VG and add the 18GB drive to it, and all 18GB will be available.

[Patrick Wallek]

Since you say you have a single VG (vg00) the only thing you can do is install Ignite/UX, if you haven't already, http://software.hp.com/product/IUX , make a make_tape_recovery tape of your system, then boot from that tape and rebuild your system.

The problem you are running into is that the paramaer Max PEs per PV (Maximum physical extents per physical volume) is too small. That parameter is set at the time that the VG is created and it is only set to the size of the largest disk in the VG (by default), which it sounds like was a 9GB disk. That parameter can NOT be modified once the VG is created.

When you rebuild the system from the Ignite/UX tape, and you include the 18GB disk in vg00 then the Max PE per PV parameter should be changed automagically to allow full use of that new disk.

I'm sure rebuilding your system is not what you wanted to hear, but unfortunately I think that's your only option.

[James R. Ferguson]

Hi Kevin:

When a volume group is first created, the maximum number of physical extents (max_pe) that will *ever* be allowed for any physical volume added will be determined from the specification of '-e max_pe' during the 'vgcreate' or from the number of physical extents on the largest physical disk used during the creation.

Once configured, you cannot change this value without recreating the volume group.

...JRF...

[Kevin Bingham]

Thanks for the swift answers, even if they contained bad news...

Whilst waiting I stumbled on the Max PE per PV value =2500, so this is clearly the problem as it limits the disk size to 10Gb, which is what I am getting...

The trouble is that we use this machine for porting work and do not have a tape device installed, so making a backup by Ignite or any other method is going to be difficult.

Is there no other way of reconfiguring the max_pe parameter for vg00? A detailed recipe would be great. I can boot from HP-UX 11.0 CD if that helps... but I guess it won't.

I obviously still have loads of space available on the new disk, can I do anything using that? (e.g. make vg01, and transfer everything there) if so, details would be nice. Consider me a novice...

TIA.
Kevin

[Sanjay_6]

Hi,

Like the others have already told you, you have hit the max PE per PV limit for your vg. If you want to add this disk to vg00 then, you have to take backups and reinstall OS.

You can see the present value of max PE using
vgdisplay /dev/vg_name

Look for Max PE per PV

Multiply that with the PE size (Mbytes) and you have the max amount of accessible disk space on any new disk that you add to this VG.

A Solution would be to add the new disk as a new VG and you can configure the MAX PE per PV limit, you may want to move it up so that you won't face any problem in adding a 36GB disk in future. I did that when i was adding a 18GB disk to my already existing VG with 9GB disk.

If you have already added the new disk to the vg you have to reduce it from them and create a new vg on this. At the time of creating a new VG on this disk add "-e max_PE_Nos" to your vgcreate command. MAX_PE_Nos >= Disk_Space (Present/Future) / PE Size

Once you are done with VG and LV creation, you can mount it anywhere you want.

Hope this helps.

Thanks

[linuxfan]

Hi Kevin,

Unfortunately the max PE gets determined at the time of VG creation, you cannot change it without recreating the VG, and in this case reinstalling the OS/reigniting it to the new disk.

The newer ignite version lets you do a make_net_recovery, so you can create an image on a different server if you don't have a local tape drive.

Another option is , if you have another disk or VG on your system, create a new filesystem and move one of the filesystems from /dev/vg00 and then you can reduce the new 18GB disk.

-HTH
Ramesh

[James R. Ferguson]

Hi Kevin:

It is preferable to place only the necessary operating system logical volumes (and primary swap) on vg00.

In my opinion, a single physical disk of 9GB is quite adequate for vg00. For performance as well as long-term maintenance, I'd backup your /apps filesystem; eliminate it from vg00; vgreduce the "new" 18GB physical disk out of vg00; create a new volume group with an appropriate logical volume for /apps consisting on the 18GB disk; and reload your data.

...JRF...

[Kevin Bingham]

Hi,

I understand that there are preferable ways of doing things, however, I was not involved in the setup of this box, it have inherited it in all its "glory"...

I need to know the following:
- how to back up without tape or Ignite
- how to restore from this backup

both of these under the circumstances that are cumulatively described above

TIA.
Kevin

[Bill Hassell]

Ignite/UX (latest version) has two commands:

make_tape_recovery
and
make_net_recovery

This means you can make a backup of vg00 over the network, then boot from the Ignite server (you'll need a lot of extra disk space) to restore vg00 again with the new disk included in vg00. Note that this is done interactively when the system boots up and the first screen of options will show you the vg00 disk...just add the additonal disk to vg00, then select the filesystem customizing tab to change the size of existing (and create new) mountpoints.

[Kevin Bingham]

Thanks to all who responded, the problem has now been resolved.
The method I used was to tar the entire LV's and FTP them off to an NT server where we had enough freespace. Then I deleted the user LV's and used vgreduce to get the new disk out of vg00. I then created vg01 specifying a BIG max_pe, re-created the user LV's in vg01, and FTP/untar'ed them back on to their new home.

I had to resort to this as the box is our only Unix box; is only used for porting work; does not have Ignite installed; does not have a DAT tape.

Kevin