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Re: WAPL panic

On Wed, Nov 07, 2012 at 02:57:46PM +0100, Edgar Fu? wrote:
> The winner was 64k fsbsize on 128SpSU (resulting in one fs block per stripe 
> unit and four per stripe).

This looks wrong.  The 6.0 kernel will never, under any circumstances,
issue a transfer larger than 64K to a disk device, not even a pseudodevice
like RAIDframe -- so this configuration guarantees that you will never be
able to do a full-stripe write, so that every write becomes a
read/modify/write cycle, tripling the I/O load.

What fragment size are you using?  Use of 64K blocks is quite rare
because the kernel already clusters I/O to 64K almost all the time for
both reads and writes, regardless of the blocksize.


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