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-------- Original message --------
From: Pádraig Brady <p...@draigbrady.com>
Date:
To: "OpenStack Development Mailing List (not for usage questions)"
<openstack-dev@lists.openstack.org>
Cc: "Day, Phil" <philip....@hp.com>
Subject: Re: [openstack-dev] [nova] - Revert change of default ephemeral fs to
ext4
> - It causes inconsistent behaviour in the system, as any existing
> "default" backing files will have ext3 in them, so a VM will now get either
> ext3 or 3ext4 depending on whether the host they get created on already has a
> backing file of the required size or not. I don't think the existing design
> ever considered the default FS changing - maybe we shouldn’t have files that
> include "default" as the file system type if it can change over time, and the
> name should always reflect the FS type.
> I'm not sure this is a practical issue since ephemeral storage is built up
> from blank by each instance
Maybe it varies by hypervisor; my understanding is that at least in libvirt the
ephemeral disks are cow layers on a shared common backing file that has the
file system in it. The naming convention includes the size and fs type or
"default" and is only created once per size-fs combination.
So this is a real issue - I think that maybe the eventual change to ext4 need
to be combined withoving away from "default" in the file name.
Phil
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