Fedora 15, new and exciting plans

Richard W.M. Jones rjones at redhat.com
Sat Nov 13 23:41:05 UTC 2010

On Fri, Nov 12, 2010 at 06:26:48PM +0000, "Jóhann B. Guðmundsson" wrote:
> *DE could consider switching the default to use EXT4 directly without 
> LVM. [1]
> 1. http://fedoraproject.org/wiki/Features/NoDefaultLVM

The "Detailed Description" seems contradictory:

| LVM provides very little benefit for most Fedora users, at the cost of
| performance and complexity:
| * Certain filesystem features (ext3 barriers) are unavailable when run
|   on top of LVM.

Isn't this just a bug which should be fixed?  (I actually thought this
had been fixed already)

| * Software RAID performance is greatly reduced when layered on LVM.

But the stated task is to get rid of LVM except for "experts in
storage administration" (from the next section of the same document).
Who will presumably be the only ones wanting Software RAID.  The
non-experts won't know anything about Software RAID, so they won't be
affected by this performance problem with LVM.

| * LVM partitions are not automatically assembled by the desktop systems.

I'm not sure what this one means.  "assembled" as in what happens when
you spread a VG over multiple block devices?

Anyway, I think LVM is jolly useful:

- You can expand the root filesystem (eg. into spare space or
across block devices).

- You can live pvmove filesystems from one device to another.

It may be that the tooling is not there to make these features
available for non-experts, but that's a problem with lack of tools,
not with LVM.  Partition tables are horrible and inflexible in
comparison to LVM.

Can we at the very least have some numbers backing up the supposed
performance problems?


Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.

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