Re: mdadm software raid + ext4, capped at ~350MiB/slimitation/bug?

[Justin Piszcz]

On Sun, 28 Feb 2010, Bill Davidsen wrote:

> Justin Piszcz wrote:
> > On Sun, 28 Feb 2010, Mike Snitzer wrote:
> >
> > > On Sun, Feb 28, 2010 at 4:45 AM, Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> 
> > > wrote:
> >
> > [ .. ]
> >
> > > How did you format the ext3 and ext4 filesystems?
> > >
> > > Did you use mkfs.ext[34] -E stride and stripe-width accordingly?
> > > AFAIK even older versions of mkfs.xfs will probe for this info but
> > > older mkfs.ext[34] won't (though new versions of mkfs.ext[34] will,
> > > using the Linux "topology" info).
> >
> > Yes and it did not make any difference:
> > http://lkml.org/lkml/2010/2/27/77
> >
> > Incase anyone else wants to try too, you can calculate by hand, or if you
> > are in a hurry, I found this useful:
> > http://busybox.net/~aldot/mkfs_stride.html
> >
> > I believe there is something fundamentally wrong with ext4 when performing 
> > large sequential I/O when writing, esp. after Ted's comments.
> >
> > Justin.
> >
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> I'm going to have to do some testing now, I just tested ext4 against the raw 
> speed of the device (single device test) and they were quite close to 
> identical. I'm going to order one more drive to bring my test setup up to 
> five devices, and do some testing on how it behaves.
>
> More later.

Thanks, let me know how it goes, I see the same thing, on a single hard 
drive, there is little difference between EXT4 and XFS:
http://permalink.gmane.org/gmane.linux.kernel/955357

However, when multiple disks are involved, it is a different story.

Justin.
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