LVM negates benefits of jounaling filesystems? [was RFE: autofsck]

[Andrew Haley]

max bianco wrote:
> On Tue, Jun 10, 2008 at 4:38 PM, Andrew Haley <aph at redhat.com> wrote:
>> max bianco wrote:
>>> On Tue, Jun 10, 2008 at 9:46 AM, Chuck Anderson <cra at wpi.edu> wrote:
>>>> On Tue, Jun 10, 2008 at 08:36:31AM -0500, Eric Sandeen wrote:
>>>>> journaling filesystem you really shouldn't have any filesystem metadata
>>>>> integrity problems on power loss; that is, if you have barriers on
>>>>> (which ext3 doesn't by default) and if your storage can pass barriers
>>>>> (which lvm doesn't), or if you have drive write cache disabled (which
>>>>> hurts performance pretty badly).
>>>> I wasn't aware that LVM destroyed the kind of guarantees about
>>>> filesystem metadata being written out to disk that jounaling
>>>> filesystems rely on?  If so, should we perhaps rethink the decision to
>>>> use LVM by default on Fedora installs?
>>>>
>>> What was the reason for using LVM in the first place. My most recent
>>> install I was really tempted to not go with the defaults but because I
>>> really don't know much about filesystems, I figured the best thing in
>>> that case was stick to the defaults. Now I am reconsidering
>>> again...could someone explain the comparative advantages/disadvantages
>>> ? Before i do something stupid .
>> LVM has a lot of advantages with regard to flexibility: you can add a
>> disk to a filesystem, for example.  It has a lot of nice features.

> but there seems to be some question as to data integrity or ability to
> recover data in the event of disaster or am i reading too much into
> this?

Yes, you are.  The question here is about barriers, which are off by
default in ext3 anyway.  If you're worried about disaster recovery, you
need to be looking at backup and replication.

Andrew.