PE Size too small - advice

[dev44]

Hi,
I have an old 11.11 system and and LV needs to be increased. The problem is that the extents are larger than the max of 65535. So normally I would vgmodify. This is 11.11 and no vgmodify, so I will have to go old-school and re-create the VG.

I figure the best way would be to create the new vg with -s 16. Then export the old vg and import the luns into the new vg. However, this is a prod system and we cannot afford any data loss or issues. So does this seem like a good way to accomplish this, or maybe someone out there has a better idea.

Thanks,
S.

[R.O.]

Hi,

I think you can ask HP Support for 11.11 vgmodify unsupported version...

Regards,

[Bill Hassell]

The PE size cannot be modified, even with the vgmodify command. This is a very common problem because the VG was probably created without any options so PE=4 MB -- way, way too small for today's disks. Never create a VG without PEsize set to at least 16, or 32 for terabyte volume groups. This is a simple bookeeping value so it has no effect on performance but it creates a hard limit to the size of disks or LUNs added to a VG.

So you are correct -- a new VG must be created, and since it is apparently growing, make PEsize=32 and also make maxPVs=32 or more. That way, you can grow this into muti-TB range without having create a new VG and move the data.

[dev44]

vgmodify, is not an option because you can't change the PE size.

My question is - do I have to create a temp VG and LVs and copy everything over. Export the old VG and then rename the filesystems on the temp to the old ones. OR - can I create a new VG with the correct parameters and then export the old VG and import the LUNS into the new VG?

[Bill Hassell]

> My question is - do I have to create a temp VG and LVs and copy everything over.

Yes.

> can I create a new VG with the correct parameters and then export the old VG and import the LUNS into the new VG?

vgimport is not a data copy command. It simply reads the existing LVM headers on the disks and connects them with lvmtab. The underlying LVM data is not changed (ie, PEsize, maxPVs, etc). vgcreate is very simple -- it connects a directory and group file in lvmtab along with defining the disk(s). You then create new lvols (typically with the same name as the original) but use the new size that you need for each lvol.

You now have two VGs, the old one with data and the new one with nothing. Create temporary mountpoints for each new lvol, then copy the data and verify the file count and directory count. Now you can umount the old and new volumes, change fstab to reflect the new VGname and mount the new lvols.

[Suraj E.M]

create new VGs with larger extent sizes and LVOLs. then copy the data from the old VGs.remove the old VGs.

[Sujit]

vgmodify is officially supported in 11.23 and 11.31, as for 11.00 not supported.

You can request 11.11 vgmodify through HP Support (unsupported version, you have log a call HP Response center.

OR
You need to create new VG & LV with new parameters & copy your data to new VG.


Sujit.

[Steven E. Protter]

Shalom,

Old school it is here, no vgmodify for 11.11

-s 16 will work.

-p will also help. The default vgcreate permits up to 255 physical volumes. Limiting the number of physical volumes does assist with this issue. Less physical volumes permits more use of larger physical volumes.

SEP