[dm-devel] [PATCHES] new barriers - 2

[Ric Wheeler]

Mike Snitzer wrote:
> On Fri, Jan 30, 2009 at 5:15 AM, Tomasz Chmielewski <mangoo at wpkg.org> wrote:
>   
>>> Here I announce 2nd version my new barrier support patches:
>>> http://people.redhat.com/mpatocka/patches/kernel/barriers/
>>>
>>> They are against 2.6.29-rc3.
>>>
>>> The most important enhancement is that with these patches, device mapper
>>> is able to send barrier requests to lower devices.
>>>       
>> I guess it still won't work for those using LVM on md (Linux software RAID)
>> because md lacks barrier support? Do you know if someone is working on it?
>>     
>
> md raid1 has supported barriers since 2.6.17
>
> But I'm not aware of any md work being done to support barriers in
> other raid levels.  Judging by Neil Brown's thoughts on the matter
> (from 2006) it would seem unlikely he is putting effort to it, please
> see the following thread:
> http://marc.info/?l=linux-raid&m=115321319003578&w=2
> http://marc.info/?l=linux-raid&m=115335249503450&w=2
>
> cc'ing linux-raid to see if others have more insight
>   

Neil, Hannes,

Is Mike's assumption above still true - no plans/thoughts about doing 
barrier support for RAID5/6 and so on?

At least some things (the null barrier op) are in place now since your 
summary of a couple years back, does this make it easier?

Thanks!

Ric