I think I figured out why I am now only able write a maximum 512K block 
size now.  Its hardware compression being enabled.  When I did my 
earlier tests, I had it turned off.


On 1/7/2010 10:01 AM, Brian Debelius wrote:
> I am just trying to understand things, so please bear with me.  I 
> understand that the recommended block size is 256K.
>
> I thought that earlier this week, I tested the LTO-3 drive with a 1M 
> block size.  But attempting to do so again, does not work.  So now it 
> looks like the actual maximum block size for the drive is 
> 512M(524288).  So now my questions.
>
> #dd if=/dev/zero of=/dev/nst1 bs=524288 count=1
> This completes successfully.
>
> If I set the Maximum Block Size = 524288 in the sd, and run btape test,
> This fails.  Why?
>
> If I set the Maximum Block Size = 523264 (1024 less) in the sd,  and 
> run btape test,
> This succeeds.  Why?
>
> If I round this block size to a 4096 division, it would be 520192.
> If I set the Maximum Block Size = 520192 in the sd, and run btape test,
> This succeeds, but it says it is using a 520092 block size  Why?
>
>
>


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