[CentOS] Tape drive throughput

[Steve]

Rodrigo Barbosa wrote:

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>On Fri, Jun 09, 2006 at 04:28:38PM -0500, Steve wrote:
>  
>
>>>Maybe you should take your time to read the manpage for "mt".
>>>Also, check the "blocksize" configuration for your tape drive.
>>>
>>>I'm not talking about cpio -C or dump -b or tar -b. I'm talking
>>>about "mt setblk" and "blocksize" for stinit.
>>>      
>>>
>>I'm quite familiar with mt's man page.   I use 'setblk 0' for my 
>>clients' backups... but for compatibility reasons, not for performance 
>>ones.  (Most OSes know about variable block size, BTW.  Even SCO Open 
>>Server.) I see no reason to turn Bowie's simple question into a "this is 
>>really complicated" answer when it's not.
>>    
>>
>
>Yes, this IS a complicated question. Not because it is "technicaly
>complicatd" but because "many factors affect it".
>
>If you use "setblk 0", you are using "Variable Blocksize". Which
>just makes it more complicated to calculate the throughput, since
>there is no way for you to know what block size will be under use
>in a given moment.
>
>But I'll give you the benefit of the doubt. Since you say it is not
>a complicated issue, please give us the throughput he is getting
>for this DLT Unit.
>
>  
>
Depends on the unit, of course.  If the OS/Software is not delivering 
something reasonably close to that in the real world, then you have a 
problem.  That's not complicated.

What Bowie asked was not what the rate was, but how he could measure 
what he is actually getting.

But I would be *very* interested to know how you could calculate the 
total throughput of a random drive if you *did* know the fixed block size.

-Steve