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Re: [linux-lvm] Horrid performance with 2.4.{9,10,12} + LVM + ReiserFS

Eric M. Hopper writes:
> On Fri, Oct 19, 2001 at 03:00:45AM +0200, Jens Benecke wrote:
> > > Well, you have 1 disk on a single channel (hda) and the other two as
> > > master and slave on *one* channel. That's the bottleneck. If the disks
> > > are accessed individually, you get the full performance (more or less).
> > > But if *both* disks have to respond, performance drops horribly.  Best is
> > > to get a third IDE controller.
> > 
> > As the disks aren't interleaved (just appended to each other) I don't think
> > this is a problem. I use LVM because I don't want to split up the FTP
> > server space with a huge chaos of symlinks and partitions, not because I
> > absolutely need RAID performance.
> 	This could still be a problem if you have two LVs on the VG that
> spans both disk, and one LV is mainly on one disk, and the other is
> mainly on the other, and you end up accessing both filesystems at the
> same time, you still get a contention problem.  This is a lot of 'ifs',
> but it can still happen.  :-)

As Eric said, appending disks does not prevent a scenario where you have
some data that spans across hdc and hdd. Or just think about the filesystem
itself. You'll never really know where files are placed on the partition...


> 	The disk space problem is the much more likely culprit.  *grin*
> Have fun (if at all possible),
> -- 
> "It does me no injury for my neighbor to say there are twenty gods or no God.
> It neither picks my pocket nor breaks my leg."  --- Thomas Jefferson
> "Go to Heaven for the climate, Hell for the company."  -- Mark Twain
> -- Eric Hopper (hopper omnifarious org  http://www.omnifarious.org/~hopper) --

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