Re: 64-bit block sizes on 32-bit systems

AJ Lewis
2001-03-26T23:05:22Z

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On Mon, Mar 26, 2001 at 11:37:52AM -0700, Eric W. Biederman wrote:
> Matthew Wilcox <matthew@wil.cx> writes:
>
> > On Mon, Mar 26, 2001 at 10:47:13AM -0700, Andreas Dilger wrote:
> > > What do you mean by problems 5 years down the road? The real issue is that
> > > this 32-bit block count limit affects composite devices like MD RAID and
> > > LVM today, not just individual disks. There have been several postings
> > > I have seen with people having a problem _today_ with a 2TB limit on
> > > devices.
> >
> > people who can afford 2TB of disc can afford to buy a 64-bit processor.
>
> Currently that doesn't solve the problem as block_nr is held in an int.
> And as gcc compiles an int to a 32bit number on a 64bit processor, the
> problem still isn't solved.
>
> That at least we need to address.

What I don't understand is why we can't just put an option in the Linux
config to enable 64-bit block support, as we have with the High Memory
Support option. That way the user could select that option if they want it,
regardless of the processor they are using. Jens Axboe <axboe@suse.de>
already mentioned he had patched the kernel to do someting similar earlier
this month on a similar thread on linux-kernel.

It makes sense to have this option when we have an enterprise level LVM
and 64-bit file systems such as the Global File System (GFS) for Linux.

Regards,
--
AJ Lewis
Sistina Software Inc. Voice: 612-379-3951
1313 5th St SE, Suite 111 Fax: 612-379-3952
Minneapolis, MN 55414 E-Mail: lewis@sistina.com
http://www.sistina.com

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