Re: "raid5: multiple 1 requests for sector ..."

[Andrew Klaassen <ak@dkp.com>]

XFS+RAID5...

Below, Neil Brown says, "If I were the author of the filesystem
I would be worried."

Are the authors of the filesystem worried?  ;)

(I'm CCing this to both the linux-xfs and linux-raid lists; hope
no-one minds...)

Andrew Klaassen


On Fri, Aug 24, 2001 at 08:21:05PM +1000, 
Neil Brown wrote:

> On Friday August 17, ak@dkp.com wrote:

> > kernel: raid5: multiple 1 requests for sector 32029440
> ...
> > kernel: raid5: multiple 1 requests for sector 40
> > kernel: raid5: multiple 1 requests for sector 76260224
> > (etc)

> On Friday August 24, eyal@eyal.emu.id.au wrote:

> > I noticed this message recently. What does it mean? Is is harmfull?
> > 
> > Running 2.4.9 with xfs.

> It means that while raid5 had an outstanding write request on a
> particular sector, it received another write request for the same
> sector.
> 
> It trys to do the right thing and write them both out in the order
> that it received them, but it is a bit of a worry that any filesystem
> would do this.  I'm guessing that Andrew is using XFS too.  Is that
> right?
> 
> While raid5 tries to keep the requests in order, and I suspect other
> drivers do to, I don't think that it is reasonable to assume that no
> device driver will ever re-order two requests for the same sector.
> If I were the author of the filesystem I would be worried.
> 
> NeilBrown