[CentOS] Disc layout advice

Ross Walker rswwalker at gmail.com
Wed Oct 7 18:18:25 UTC 2009


On Tue, Oct 6, 2009 at 3:58 PM, Stephen Harris <lists at spuddy.org> wrote:
> On Tue, Oct 06, 2009 at 07:29:00PM +0000, Joseph L. Casale wrote:
>> >You don't run pvcreate on lvm partitions.  You run pvcreate on the block
>> >devices that will be added to the volume groups.
>>
>> You sure can run pvcreate on a partition, for example /dev/cciss/c0d0p1
>
> c0d0p1 is not an LVM partition.  It's a disk partition.  Be careful of
> terminology.

Hehe, LVM doesn't have partitions it has logical volumes, so...

> The *next paragraph* of the email you replied to said
>  "Now these block devices could be a hard disk partition"
>
> If you look at /dev/cciss/c0d0p1 then you'll see it's a block device.
> ("ls -l" and you'll see the first character is a "b").  A partition is
> a specific type of block device.

Yes, a partition is a block device with an offset and size. Joseph
knows his stuff he's been on list for a while now just looking for
confirmation.

> However, the point of my email is the level that you think of it.
> If you think in terms of devices then you don't get any confusion
> (so no questions such as "do I need to partition my md disk for lvm?")
> because you're thinking in terms of how the technology works.  Your "md"
> raid device, your disk partition, your whole disk... they're all just
> block devices.


Joesph,

You can create PVs out of any block device (even LVs).

You don't need to partition past the raw device storage, even that is
optional, but recommended so other OSs know that, yes the space is
actually used, if your using a volume manager like LVM. If you need to
create a partition on a raw multi-terabyte device, you will need a GPT
partition table as MBR stops working at 2TB I believe.

-Ross


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