Zitat von Alan Brown <ajb2 AT mssl.ucl.ac DOT uk>:

> On 21/08/12 12:27, lst_hoe02 AT kwsoft DOT de wrote:
>
>> So i still wonder why the manual recommend not to change this value?
>
> Because some (older) drive types don't like it and will break.

Of course but the manual as far as i understand explicitely discourage  
altering the value for Block Size with modern hardware: "On most  
modern tape drives, you will not need to specify this directive.."
So it should be more of don't alter this value for old tape drives and  
don't alter the value after first tape usage or you will not be able  
to restore.

>> The problem of not mixing the blocksize is obvious so if there is not
>> other downside one should choose a larger value with any recent tape
>> drive, no?
>
> It's only obvious to those experienced with tape. Inexperienced  
> admins are likely to end up with non-restorable tapes due to mixed  
> blocksizes on one volume and not realise what they've done until  
> it's far too late.

Given the complexity of backup/restore and the knowledge required a  
big *warning* in the manual should be sufficient i guess...


> LTO drives can handle blocksize up to 16Mb. I suspect that moving to  
> 4 or 8Mb would result in better throughput but that isn't an option  
> at the moment.
>
> Similarly, the 64kb network block size isn't really large enough for  
> Gb/10Gb-scale networks but in my experience setting larger values  
> causes problems inside bacula.
>
> Alan

With this in mind i really wonder how many Bacula installations setup  
the last 5 years are running with shoe-shining tape drives despite the  
fact that Bacula can do better.

Thanks for your help on this one

Moving to next part of the puzzle ;-)

Andreas




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