Re: [linux-lvm] md + lvm + reiser

[Chris Jantzen <chris@maybe.net>]

On Mon, Sep 09, 2002 at 12:04:11AM +0200, Luca Berra wrote:
> On Sun, Sep 08, 2002 at 11:44:41PM +0200, Xavier Montagutelli wrote:
> >On Sat, 7 Sep 2002, Chris Jantzen wrote:
> >
> >>VFS lock patch, yes, but my real question is: why is the raid5 buffer
> >>cache constantly thrashing back and forth? I assume this has to do with
> ...
> >I have exactly the same symptoms with the same configuration (md + lvm +
> >reiser) ; the raid5 cache size keeps changing when I start using
> >snapshots. Does someone have some tips to avoid/explain this ?
> 
> The r5 cache needs a fixed request size, Neil once explained me, but i
> do not recall the exact details now, when the md layer receives a
> request with different size, it has to be emptied and recreated with
> the new size.
> This is the meaning of the message, it is harmless, except for
> performance, at the moment the best that can be done about it is
> commenting out the message.


Well, I know it's harmful and I know that's exactly why it happens. I
want my performance though! :-) I was wondering if any of the deep LVM
guru's could say whether SECTOR_SIZE could be safely bumped up. Thanks
for the input and I think I'll wait a few more days before making a hard
decision.

-- 
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Insert witty comment here.     _`\<,_
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