CentOS - Oct 2009 - adding SAN "diskspace" to CentOS system residing on VMware

Hey, group,

I've got a system installed on a VMware VM.  The SAN administrator
allocated me more disk space from the (EMC) SAN and I need ultimately to
create another partition to mount on the filesystem.  Two (initial)
questions about this:

What steps do I need to take prior to creating a new partition with
fdisk?  (The SAN space, BTW, is connected through VMware.)

The OS is already residing on a logical volume.  Is there any compelling
reason to bringing the new partition into lvm (aside from the ease of
resizing it... something I don't anticipate us doing)?  Or should I
simply create an ext3 partition and mount that?

Thanks much.

On Fri, Oct 30, 2009 at 2:10 PM, ken <gebser at mousecar.com>
wrote:
> Hey, group,
Hi.
> What steps do I need to take prior to creating a new partition with
> fdisk? ?(The SAN space, BTW, is connected through VMware.)
How's the storage being exported?

-jonathan

ken schrieb:
> Hey, group,
> 
> I've got a system installed on a VMware VM.  The SAN administrator
> allocated me more disk space from the (EMC) SAN and I need ultimately to
> create another partition to mount on the filesystem.  Two (initial)
> questions about this:
Given with "VMware VM" you mean a virtual machine on an ESX(i) system
and that the admin just increased the disk size for the VM, you will see
the additional disk space using fdisk / cfdisk as unallocated space.
Either increase your LVM or create a new partition.
> What steps do I need to take prior to creating a new partition with
> fdisk?  (The SAN space, BTW, is connected through VMware.)
> 
> The OS is already residing on a logical volume.  Is there any compelling
> reason to bringing the new partition into lvm (aside from the ease of
> resizing it... something I don't anticipate us doing)?  Or should I
> simply create an ext3 partition and mount that?
Depends much on the purpose of the additional space. Generally LVM makes
it very easy to increase any of the existing LVMs / mountpoints.
> Thanks much.
Alexander

If you are a good little doobie, check with your san admin to see if you
need to change your starting block alignment. If he looks at you funny,
take everything the man says to you with a grain of salt for the rest of
your life. 

http://www.vmware.com/pdf/esx3_partition_align.pdf

Patrick
> -----Original Message-----
> From: centos-bounces at centos.org 
> [mailto:centos-bounces at centos.org] On Behalf Of ken
> Sent: Friday, October 30, 2009 3:10 PM
> To: CentOS Mailing List
> Subject: [CentOS] adding SAN "diskspace" to CentOS system 
> residing on VMware
> 
> Hey, group,
> 
> I've got a system installed on a VMware VM.  The SAN 
> administrator allocated me more disk space from the (EMC) SAN 
> and I need ultimately to create another partition to mount on 
> the filesystem.  Two (initial) questions about this:
> 
> What steps do I need to take prior to creating a new 
> partition with fdisk?  (The SAN space, BTW, is connected 
> through VMware.)
> 
> The OS is already residing on a logical volume.  Is there any 
> compelling reason to bringing the new partition into lvm 
> (aside from the ease of resizing it... something I don't 
> anticipate us doing)?  Or should I simply create an ext3 
> partition and mount that?
> 
> Thanks much.
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
> 
>

On Fri, Oct 30, 2009 at 2:10 PM, ken <gebser at mousecar.com> wrote:
[snip]
> The OS is already residing on a logical volume. ?Is there any compelling
> reason to bringing the new partition into lvm (aside from the ease of
> resizing it... something I don't anticipate us doing)? ?Or should I
> simply create an ext3 partition and mount that?
Using LVMs also gives you a lot of flexibility in moving volumes
around. For example, you may later upgrade your SAN. If you have LVMs
you can transparently mirror one SAN volume to another and then remove
the original. You can do this with standard partitions, but the
process requires some downtime.

LVMs can allow snapshots, which are quite useful in many situations.

On Nov 2, 2009, at 10:15 AM, "Flaherty, Patrick" <pflaherty at
wsi.com>
wrote:
> If you are a good little doobie, check with your san admin to see if  
> you
> need to change your starting block alignment. If he looks at you  
> funny,
> take everything the man says to you with a grain of salt for the  
> rest of
> your life.
>
> http://www.vmware.com/pdf/esx3_partition_align.pdf
Always hedge your bet and start your partitions at 1MB offset, that  
should cover most chunk sizes.

With LVM make sure you build into the PVs the offset. I believe the  
metadata is 128K and the first LV is an additional 64K offset, making  
the data start at 192K. Fine if your stripe chunk size is 64K, but to  
cover all the possible chunk sizes make the metadata size 1MB minus  
64K during pvcreate. I also set metadatacopies to 2 so there is a  
backup.

-Ross