Re: [Aoetools-discuss] active/active aoe + raid0

[Matthew I. <ma...@di...>]

On Oct 15, 2009, at 9:55 AM, Matthew Ingersoll wrote:

>
> On Oct 15, 2009, at 8:19 AM, Ed Cashin wrote:
>> What am I saying?  The main problem is the page cache.  The I/O for
>> the components of the RAID 0 will go through the page cache on each  
>> of
>> the two AoE initiators, and without some way for the two hosts to  
>> make
>> sure that the page cache contents match (e.g., "I just changed the
>> data here---update your cache!") the scenario won't work.
>
> At what layer(s) does page cache come into play?  I know the gist of
> how it functions but not the dirty details.  I thought it only came
> into play when using a filesystem?
> For example, if the controllers shared a block device using vbladed,
> running with direct io wouldn't ensure consistency on both  
> controllers?
>

And what about the buffer cache? Does direct/O_DIRECT mode bypass this  
also?
 From the setup I described there are no filesystems and page cache  
wouldn't play a role but buffer cache would (right?).

--
Matth