Max disks in a vg

[Nobody's Hero]

I have an older symmetrix EMC box, 1tb of 4gb drives. I want to add a large amount of disks into one volume group. What kern parm do I change to allow this? Is it safe to enter a large amount of disks into a VG. I will be adding about 60 drives into this vg.

thx
RPM

[Pete Randall]

Robert,

First thing to look at is the pvcreate command and it's -p option, which defines the maximum number of physical volumes in the VG. Default is 16, and the max is 255.



Pete

[Nobody's Hero]

Can I change this when I am creating the disks if I am using sam?

[RAC_1]

You can set while creating vg with -p option.

Check man vgcreate.

[Ian Dennison_1]

This value (Max Phys Volumes) can only be set at vgcreate time, along with the Maximum Disk Size.

So be sure to add the biggest disk and highest resonable Max Phys Vol) during the 'vgcreate' command (not the 'pvcreate' command as specified by Pete).

Share and Enjoy! Ian

[Tom Danzig]

No kernel parameters need be changed. You set this when you create the volume group using the "-p max_pv" parameter. I believe the max is 255. The default is 16. If the volume group already exists and the number is not large enough, I'm afaid you'll need to recreate the VG. Sorry :(

You could ask EMC to bind these smaller LUN's into a larger metaluns which could get you out of recreating the VG. It's a bin file change though and that costs $$$

[Nobody's Hero]

Thanks all, but can I change the value using SAM ???

[James R. Ferguson]

Hi Robert:

When you issue the 'vgcreate' command you will need to specify the larger number of disks you intend to add to the volume group. The '-p max_pv' argument defines this value. If you fail to use this argument, your volume froup will be limited to 16 physical disk. The 'vgcreate' is easily done at command line following a 'pvcreate'.

Regards!

...JRF...

[Helen French]

No kernel parameter for Maximu PVs (it's only for max VGs). But you need to give a max. PV number when you create the VG with -p option:

# vgcreate vg_name -p max_pv ..other options ..

Also, if you want to add higher capacity disks in future, change the pe_size too, with -s option. It's not a big deal to add more disks in to a VG, the VG will acitvate if the quorum is present. But when you create LVs, I wouldn't add a large number of disks in a single LV since a failure of a single disk will cause the entire failure of that LV. You need to re-create(vgcfgrestore and newfs) and restore the data in that case.

[S.K. Chan · Accepted solution]

In Sam you would go to ..
Disk&Filesystem->VolumeGroups
Go to the Action Tab and select "Create" and you'll be prompted for ..
a) New VG Name
b) Select Disk
c) Modify Default VG Option
- Max PE
- Max LV
- MAX PV
- PE Size
In c) is where you enter your max PV.

[Pete Randall]

Sorry, Robert - I meant vgcreate but my stupid fingers weren't listening!

Pete

[John de Villiers]

Ask you EMC rep if they cannot config all your disks into one biggish metavolume. That way you only see one disk on you host. the striping and raid and everything is done by the EMC

[John Meissner]

I recently discovered this (the hard way)

with a PE size of 8 the max number of PE's you can have is 146 - in order to utilize the maximum number of PE's possible you will need to have a PE size of 16 which will allow you to have 255 PE's.

I was working on a script and ran into this problem and had to call HP to get the answer. I should have just posted here instead :)