[linux-lvm] Software RAID 5 Resizing and LVM

Garrick Staples garrick at usc.edu
Sat Nov 20 08:38:08 UTC 2004

> Date: Wed, 17 Nov 2004 10:53:00 -0600
> From: Jetkins at austinlogistics.com
> Subject: Re: [linux-lvm] Software RAID 5 Resizing and LVM
> To: adam at slackguy.net
> I asked pretty much that exact question on Monday! :)  The only difference
> was that mine is a hardware RAID.  Someone replied with a possible
> workaround if you're using LVM2, but if you're using LVM1 like me, and you
> pvcreate'd your PV across the entire disk like me, then you're screwed like
> me. :(
> If you partitioned the logical disk and pvcreate'd a partition, then you
> should be able to create a new partition on the newly-available space, then
> pvcreate a second PV and add it into the VG.  The wonders of 20/20
> hindsight.

I'm using the entire, unpartitioned, block device on my boxes on advice from my
DataDirect Networks vendor.  Apparently putting a partition table at the front
of the block device offsets each write request 512 bytes, which is disasterous
for performance.  By using the whole device, the writes are correctly byte
aligned to the arrays.

Garrick Staples, Linux/HPCC Administrator
University of Southern California
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