linux-ext4 - Re: I/O topology fixes for big physical block size

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Message-ID: <20100930173342.GB31945@redhat.com>
Date:	Thu, 30 Sep 2010 13:33:43 -0400
From:	Mike Snitzer <snitzer@...hat.com>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	"Ted Ts'o" <tytso@....edu>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Jens Axboe <jaxboe@...ionio.com>,
	"James.Bottomley@...senpartnership.com" 
	<James.Bottomley@...senpartnership.com>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: I/O topology fixes for big physical block size

On Thu, Sep 30 2010 at  1:07pm -0400,
Eric Sandeen <sandeen@...hat.com> wrote:

> On 09/30/2010 11:30 AM, Ted Ts'o wrote:
> > On Tue, Sep 28, 2010 at 04:36:42PM -0500, Eric Sandeen wrote:
> >> Ok, then it sounds like mkfs.ext4's refusal to make fs blocksize less
> >> than device physical sectorsize without -F is broken, and that should
> >> be removed.  I'd say issue a warning in the case but if there's a 16k
> >> physical device maybe there's no point in warning either?
> > 
> > If the device physical sectorsize is that big, should we perhaps use
> > that as a hint to align writes to that blocks aligned with that
> > physical sectorsize?  Right now we use the optimal I/O size, but if
> > the optimal I/O size is not specified and the physical sectorsize is,
> 
> I can't keep track of all the parameters, is it ever true that optimal
> I/O size isn't specified?

Yes optimal_io_size may be 0.  But minimum_io_size will always be scaled
up to at least match physical_block_size.

In any case: this 1MB physical_block_size device, which started this
thread, also has 1MB for both minimum_io_size and optimal_io_size.

Mike
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