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

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.


>>> "partitioning is obsolete" ;-)
>> LVM is nothing but a partition manager...
> 
> LVM is more than a partition manager:

I am well aware of what LVM2 and device mapper can do.

	Jeff