[Beowulf] Sidebar: Vista Rant

jason bishop jason.bishop at clustercorp.com
Thu Jul 19 13:13:30 EDT 2007


On Jul 19, 2007, at 1:34 AM, Tim Cutts wrote:

>
> Those look like much the same caveats to me.  At least later  
> versions of Mac OS X supply the fcntl() methods to specifically ask  
> the driver to commit (although how it can possibly guarantee that I  
> don't know - the device could be a long way away across a SAN);  
> that possibility does not exist on Linux, as far as I know,  
> although I'm willing to be corrected.
>
> Any code that relies on sync(), or any other method which just  
> results in a *request* to flush the data to the physical storage,  
> is going to have small windows where the data is at risk.  Enter  
> UPS, stage right.  :-)
>
> Mind you, MySQL is perfectly capable of corrupting its own data  
> without relying on rare hardware and power failures to blame for it.
>
> Tim

a bunch of work on i/o barriers (FUA) was done a while back on the  
linux side.  (i'm not sure about a special fcntl call.  that sounds  
strange).  fua was even plumbed into some userspace utils (ie:  
sg_dd), but i haven't kept up with it to see if its actually achieved  
end-to-end yet, and if so, on what hardware.

jason

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