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Re: XFS + LVM + Epanding; shrinking XFS??

To: Austin Gonyou <austin@xxxxxxxxxxxxxxx>
Subject: Re: XFS + LVM + Epanding; shrinking XFS??
From: "Martin K. Petersen" <mkp@xxxxxxxxxxxxx>
Date: 10 May 2001 11:20:33 -0400
Cc: <linux-xfs@xxxxxxxxxxx>
In-reply-to: <Pine.LNX.4.33.0105100950540.24470-100000@xxxxxxxxxxxxxxxxxxxxxxxx>
Organization: Linuxcare, Inc.
References: <Pine.LNX.4.33.0105100950540.24470-100000@xxxxxxxxxxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
User-agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.4 (Copyleft)
>>>>> "Austin" == Austin Gonyou <austin@xxxxxxxxxxxxxxx> writes:

Austin> Seems a bit odd here if I want to create a striped set, it
Austin> seems that you must create several "groups" of single disks
Austin> and then when using lvcreate stripe those "Groups". Thoughts?

Nope.  A volume group is a set of disks that you decide to put
together for administrative purposes.  Usually a either the internal
disks or an external disk array.  Grouping disks makes it easier to
move them between machines.  And you might have different requirements
for different types of data.

A volume group consists of physical volumes (PVs) which are physical
disk partitions in most cases.

Each PV is chopped into fixed-size chunks (Physical Extents).  Default
is 4MB.  See the vgcreate manpage for more info.

When you create a logical volume you have two choices:

If you don't specify striping parameters, the allocator will pick
whatever free PEs it feels like and use those.  It will round the size
you specify for your partition to a PE boundary.

If you do specify striping parameters, the allocator will interleave
the PEs spreading out your logical volume over the available PVs.  And
it will do striping with your preferred stripe size on top of those

I suggest you read the LVM Howto:


And for a brief hands-on striping setup, there's the blurb I wrote for
use with XFS way back.  Note that this was written before I
implemented the LVM interface, so you can't see mkfs.xfs extract
stripe info from the logical volume in that document.  But that works
without user intervention these days.


Martin K. Petersen, Principal Linux Consultant, Linuxcare, Inc.
mkp@xxxxxxxxxxxxx, http://www.linuxcare.com/
SGI XFS for Linux Developer, http://oss.sgi.com/projects/xfs/

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