Re: [Ext2-devel] [RFC 0/13] extents and 48bit ext3

[Laurent Vivier]

Jeff Garzik wrote:
> Laurent Vivier wrote:
>> Jeff Garzik wrote:
>>> Laurent Vivier wrote:
>>>> Qi Yong wrote:
>>>>> Linus Torvalds wrote:
>>>>>
>>>>>> On Fri, 9 Jun 2006, Stephen C. Tweedie wrote:
>>>>>>  
>>>>>>
>>>>>>> When is the Linux syscall interface enough?  When should we just
>>>>>>> bump it
>>>>>>> and cut out all the compatibility interfaces?
>>>>>>>
>>>>>>> No, we don't; we let people configure certain obsolete bits out
>>>>>>> (a.out
>>>>>>> support etc), but we keep it in the tree despite the indirection
>>>>>>> cost to
>>>>>>> maintain multiple interfaces etc.
>>>>>>>   
>>>>>> Right. WE ADD NEW SYSTEM CALLS. WE DO NOT EXTEND THE OLD ONES IN
>>>>>> WAYS THAT MIGHT BREAK OLD USERS.
>>>>>>
>>>>>> Your point was exactly what?
>>>>>>
>>>>>> Btw, where did that 2TB limit number come from? Afaik, it should be
>>>>>> 16TB for a 4kB filesystem, no?
>>>>>>  
>>>>>>
>>>>> Partition tables describe partitions in units of one sector.
>>>>> 2^(32+9) = 2T
>>>>>
>>>>> To prevent integer overflow, we should use only 31 bits of a 32-bit
>>>>> integer.
>>>>> 2^(31+12) = 8T
>>>>>
>>>>> There's _terrible_ hacks to really get to 16T.
>>>>>
>>>>> -- qiyong
>>>>>
>>>> IMHO, a simple solution is to use "Logical Volume Manager" instead of
>>>> partition
>>>> manager: we create 64bit filesystem in a Logical Volume, not in a
>>>> partition.
>>> That doesn't solve anything, if you are not using a 64bit filesystem.
>>
>> Sorry, I don't undestand why ???
>>
>> You can use 32bit filesystem too, but you limit the size of the
>> logical volume
>> to be compatible with the filesystem you use. LVM allows to create
>> several 32bit
>> volumes on a big (> 8T) disk (if exists)
> 
> Let's review the thread:
> 
> qiyong: <these limits> exist in the filesystem
> you: bust those limits with LVM!
> 
> I think you are misunderstanding the subthread.
> 

Yes...

I understood:
qiyong: <these limits> exist in the partition manager.

(because with patches proposed on http://www.bullopensource.org/ext4 these
limits don't exist anymore in the filesystem.)

Regards,
Laurent
-- 
Laurent Vivier
Bull, Architect of an Open World (TM)
http://www.bullopensource.org/ext4

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