[CentOS] ext4 in 5.3

Peter Kjellstrom cap at nsc.liu.se
Fri Jan 23 14:56:07 UTC 2009


On Friday 23 January 2009, Stephen John Smoogen wrote:
> On Tue, Jan 20, 2009 at 9:11 PM, Stephen John Smoogen <smooge at gmail.com> 
wrote:
> > On Tue, Jan 20, 2009 at 6:33 PM, Jerry Geis <geisj at pagestation.com> wrote:
> >> Hi guys - I'm really looking forward to 5.3 for the potential of ext4.
> >> I am moving/copying image files lately 8G file and it is slow. I am
> >> hoping that ext4 really speeds that up.
> >
> > I don't think it will speed things up much. 8GB files are mostly
> > hardware throughput and ext3/4 will actually be slower because the
> > journalling etc are to make it more robust but at a speed cost. You
> > would probably see better speed by going to ext2.
>
> I make it a habit of eating my own words if I screw up. If the results
> seen on Ubuntu by one test hold up, it might have a large increase in
> large writes

In my experience write performance for different filesystems is very dependant 
on the type of hardware. I have raid controllers where the difference between 
Ext3 and XFS is ~20% and I have those where it is 120%...

> (but nothing in large reads). 

Read (single thread seq.) is often limited by having a too low read ahead 
setting. "blockdev --setra 8192" can often push it up to bare metal speed for 
both Ext3 and XFS. It's important to note that this may not be very optimal 
for your typical I/O mix (non single thread, non seq.).

/Peter
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