On Mon, Jul 14, 2003 at 11:49:14AM +0930, Greg 'groggy' Lehey wrote:
> On Sunday, 13 July 2003 at 20:57:46 -0500, Marc Wiz wrote:
> > On Mon, Jul 14, 2003 at 10:02:58AM +0930, Greg 'groggy' Lehey wrote:
> >>> I don't believe vinum can optimize full-stripe writes, though, since
> >>> FreeBSD can only do I/O in 64k max chunks,
> >>
> >> 128 kB.
> >
> > I thought physio was limited to 64 KB?  The man page on dump states
> > this.  Please correct me if I am wrong.
> Physio is limited to MAXPHYS, which you'll find defined in
> /usr/include/sys/param.h:
>   #ifndef MAXPHYS
>   #define MAXPHYS             (128 * 1024)    /* max raw I/O transfer size */
>   #endif

That's nice to know.  What prevents it from being increased beyond

> I've taken a look at the dump code (yuk!), and it no longer places any
> limitation on the block size.  I'll fix the man page.

Thanks.  I have tried increasing the block size but going past 64K
does not seem to help performance.  I will have to check the dump
code to see if it is limiting itself to a max of 64K.



Marc Wiz
Yes, that really is my last name.
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