[rhelv6-beta-list] Volume management with btrfs (and LVM) --WAS: My first experiences with RHEL6 beta

[Bryan J Smith]

PEs are never fragmented, wholly unlike filesystems.
PEs are always contiguous, possibly not physically linear,
but they are always contiguous.
This is yet another meta-argument that is non-real-world.

Now if someone doesn't know what they are doing with LVM,
and starts doing things that are laughable, then yes, we consulants
coming in and having to move around PEs to correct the issues
can be a PITA.  E.g., adding a PV to a VG that is striped and
allocated into LVs, and then extending into the non-striped PV.

LVM is cake to use in replace of legacy, hardware-specific disk
labels and offers numerous advantages.  But the more performance
features one takes advantage in with LVM, the more one has to
ensure they allocate correctly for optimal performance.
But even if they don't, in the overwhelming majority of cases
the "worst case scenario" is "as slow as legacy disk labels."

Any more fringe, hypothetical scenarios based on (incorrect)
assumptions?  (did I respond to another meta-discussion comment)?


--  
Bryan J Smith - mailto:b.j.smith at ieee.org  
http://www.linkedin.com/in/bjsmith
Sent via BlackBerry from T-Mobile  
    

-----Original Message-----
From: Chris Adams <cmadams at hiwaay.net>
Date: Wed, 16 Jun 2010 10:34:56 
To: Red Hat Enterprise Linux 6 (Santiago) Beta releases discussionmailing-list<rhelv6-beta-list at redhat.com>
Subject: Re: [rhelv6-beta-list] Volume management with btrfs (and LVM) --
	WAS: My first experiences with RHEL6 beta

Once upon a time, Bryan J. Smith <b.j.smith at ieee.org> said:
> > - Lack of advanced tools: Bryan mentioned moving PEs
> > around, but right now that's a PITA.  If you want to "defrag"
> > your LVs,
> 
> Defragmentation is a function of the filesystem and, just like
> resizing the filesystem, have nothing to do with LVM or volume
> management.  This is the same on_all_ OSes.  ;)

You mis-understand: I mean defragmenting the PEs in your LVs.  If you
have LV#1 followed by LV#2 followed by LV#3, and then you extend LV#2
into free space after LV#3, you may want to move the PEs around such
that all of LV#2's PEs are contiguous again (e.g. for performance).

AFAIK the only way to do that today is to have another PV in the VG and
move LVs back and forth.
-- 
Chris Adams <cmadams at hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.

_______________________________________________
rhelv6-beta-list mailing list
rhelv6-beta-list at redhat.com
https://www.redhat.com/mailman/listinfo/rhelv6-beta-list