block alignment

[Ric Wheeler]

On 01/07/2013 04:33 PM, Bradley C. Kuszmaul wrote:
> What is the largest data block size that I'm likely to run into with xfs?
>
> I ask, since I'm doing hole punching, and I don't want to incur the I/O 
> required to zero unaligned boundaries.  So I want to keep the holes I punch 
> sufficiently well aligned.
>
> -Bradley
>

I think that you really need to worry about the block sizes below XFS - the 
storage block size specifically. Upstream (and modern distros like 
RHEL/SLES/etc) do work to export out alignment requirements and optimal IO sizes.

You can find them in /sys/block/sda/. Martin Peterson wrote up a good overview 
of what we have in there:

https://oss.oracle.com/~mkp/

Ric