Re: journal size reiserfs vs reiser4

[Hans Reiser <reiser@namesys.com>]

Peter Staubach wrote:

> Hans Reiser wrote:
>
>>>>>       
>>>>
>>>> Wow.  What is all that space used for?  Other journalling file
>>>> systems that
>>>> I have seen have limited things like journals to a much smaller space,
>>>>     
>>>
>> BSD FFS has a 10% limit unless you are root.  They are correct to do so.
>>
>
> Yes, they reserve that space so that their algorithms to choose blocks
> from
> the various cylinder groups can continue to choose blocks in decent
> locations.
> BSD FFS doesn't journal though.
>
> The SunOS UFS does journal metadata and retains the same 10% limit. 
> It was
> discovered that the journal didn't need to be very big in order to
> maximize
> performance though.  A very small log would do as well as a very large
> log.

Journaling, and reserving space for good allocation, are totally
different concerns, I don't understand why you guys are conflating them.

>
> It would be interesting to pick a benchmark which represents some market
> that usually deploys reiersfs and then experiment with various aspects of
> the file system, including the reserve space.  It is easy to do, mostly
> just time consuming and requires a fair amount of resources.
>
>       ps
>
>