Thanks - one last question

[Jeff Ohlhausen]

Any thoughts on the optimum parameters for lv and vg creation?

Thanks again,
Jeff

[Pete Randall]

Jeff,

It really depends on your situation - the one thing(s) I would look out for is pe_size and max_pe in the vgcreate because if you want to add larger disks to this vg at a later date, you will probably not be able to if you allow these values to default.


Pete

[Tim Sanko]

I tend to make vg001 associated with lvol001, vg002 to use vg002 and the mount points are /d001 and /d002 respectively.
lvol003 with /d003. If I make striped metas on the sym they have an m in them. lvolm03 concatted metas are lvolc004 and mounted as /d004c /d004m. the last three digits are necessary because we tend to use 8-128 GB hypers or metas for our database storage.

Isn't that useful?

Tim

[Tim Sanko]

Now I am scratching my head. I realize now that with the Symmetrix raids I have used I have a wealth of storage that rarely comes into play.


I manipulate my storage on the raid, less often on the HP. I prefer striped metas to merely individual hypers, for performance sake. then I bcv the whole schebang.

I understand being careful with pemax, but depending on your storage it may not be relevant...

Tim

[Sridhar Bhaskarla]

Hi Jeff,

I usually try to specify "MAX PV" and "Max PE Per PV". PE size is dependent on the above.

Max PV - This will allow me to add more PVs to the VG later. By default this parameter is set to 16.

Max PE per PV - This parameter will decide how big a PV you can add it to the VG. For ex., if you created a VG with a 4 GB disk with a 4 MB extent size with default options, the "Max PE per PV" is set to 1000. This means, if you add a bigger disk later, you can only get 1000 PEs out of it which means it is limited to only 4 GB. So, you could specify a non-default number for this parameter during the creation so that you could add bigger disks later.

PE Size: You will need to adjust it based on the above settings.

vgcreate won't work unless it is default (not recommended) and it is a correct combination of Max PE, Max PV and PE size.

-Sri

[Tim D Fulford]

How long is this piece of string...

What I've come to do.
1 - Determine likely maxium VG capacity. We use informix and in versions less than 9.4 there is a 2GB limit. Each VG has a limit of 255 logical volumes. This means there is a practicle limit of 500GB of usable space for the VG

2 - For migration purposes I like to make MAX PE per PV DOUBLE the largest disk in the VG

3 - For migration purposes, I like to make sure the number of MAX PV per VG is TWICE the current numbers of disks.

points 2 & 3 allow you to add disks into the volume group & mirror the data on-to them (then decommision the old disk say)

Unfortunately without much history you will be guessing, but the above will give you some room for manouver in expanding or migrating the volume group.

Regards

Tim