[Lustre-discuss] llapi stripe_size

[Andreas Dilger]

On 2010-04-16, at 11:07, burlen wrote:
> calling llapi_file_create reports the following error:
>
> error: bad stripe_size 4096, must be an even multiple of 65536 bytes:
> Invalid argument (22)
>
> The operation manual said: This value must be an even multiple of  
> system
> page size, as shown by getpagesize. The value 4096 above was returned
> from a call to getpagesize. (I don't intend to set the stripe size so
> small, this is just to illustrate).
>
> Where does the number 65536 come from, what's the right way to  
> determine
> it at runtime?


The manual is incorrect in this case.  The correct limit is 65536  
bytes, not 4096.  It _used_ to be 4096 bytes, but since Linux supports  
client PAGE_SIZE up to 65536 bytes, and the VM cannot partially dirty  
a page, we do not support a stripe size that is smaller than a single  
page.

Cheers, Andreas
--
Andreas Dilger
Principal Engineer, Lustre Group
Oracle Corporation Canada Inc.