[linux-lvm] lvm2: zeroing free space

Bryn M. Reeves bmr at redhat.com
Fri Feb 4 14:12:03 UTC 2011

Hi Folks,

Recently had a query from someone using an array supporting thin provisioning
with zero page reclaim[1].

They wanted a method to write zeros to all the unallocated space in a VG to
trigger a reclaim of unused regions in the VG's PVs.

My suggestion was to lvcreate a -l100%FREE LV named "filler" and overwrite it
from /dev/zero.

It seems like this might something a lot of users want as this functionality
gets to be more common.

I wondered if it could be worth adding a script to automate this or even an
option to vgchange (e.g. --zero-free-space)?

Didn't have time to try putting anything together yet but it seems such a
feature could be useful.


[1] http://blogs.hds.com/hu/2009/03/zero-page-reclaim.html

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