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SubjectRe: VFS 64-bit clean? Not yet (was Re: large-file-system)

>>> It can. NFS V3 is 64bit and needs to put 64bit values in
>>> the page cache to get full results.
>>
>> But does it need to store _arbitrary_ 64-bit values, or does
>> it just need to store the offsets of the mapped pages used by
>> the given Linux machine? If the latter, then the original plan
>> would have worked, up until someone accessed a 1024G file.
>
> Think *HUGE*. I know people working with files, not filesystems
> of that size, though not under Linux and not via NFS.
>
> In fact there are installations like the weather data archives
> at the DWD where the total archived data's size will in just
> _few_ year reach the 64bit limit.

OK, this is getting silly.

Places that have space for such huge files can afford to hire
a team of developers, buy source for any Unix they want, etc.

The rest of us would like to NOT see performance go to hell.
It would be nice to be able to master a DVD disk. That requires
only 2 to 4 bits more than we have now. Going with signed sectors
would be 9 more bits. Remember, this is exponential expansion.

Sure, you can reach even a 63-bit limit with sparse files.
You can reach a 1023-bit limit that way too, so who cares?
Such software is severely broken, for several reasons:
1. filesystems like ext2 must use triple-indirect blocks and worse
2. such software can't run on systems with a 32-bit limit
3. such software can't run on all filesystems

It is important to use sectors, so that filesystems that allocate
by the individual sector won't become gross hacks. SGI's EFS is
such a filesystem. Unaligned filesystems are also a problem.

Going with signed sector numbers allows for efficient error
return codes. It is the normal "C" method.

Grand visions of a solution for all time are just not practical.
I've heard that fixing the year 2000 problem is _cheap_ compared
to all the memory (core!) saved.

Practical solutions satisfy everyone stuck using 32-bit hardware.
I'm sure the weather service is using Alphas and I'm sure that
demanding Linux users will have 64-bit Intel hardware in 3 years.

That is the real need of course: last until we have 64-bit CPUs.
By the time 1 TB limits are a problem, the limit will be gone.


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