max partition size

max partition size

[Michal Jaegermann]

Who knows for sure what is the current upper limit on ext2/ext3
file system size (4KiB blocks as this is what tools will accept)?  It
definitely is not 1 TB as we were making working partition nearly twice
that.  But practice seems to indicate that 2 TB, or whereabout, can be
too much.  Is this a property of a file system or we bumping into
block device boundaries or this are just tools?

BTW - mke2fs goes most of the way but gets stuck eventually when
writing inode tables if that it is too close to 2 TB.  Yes, there
are people who really want that much of a file system or maybe even
more. :-)   This was not done for a sake of a record.

  Michal

Re: max partition size

[Andreas Dilger]

On Mar 22, 2002  00:50 -0700, Michal Jaegermann wrote:
> Who knows for sure what is the current upper limit on ext2/ext3
> file system size (4KiB blocks as this is what tools will accept)?  It
> definitely is not 1 TB as we were making working partition nearly twice
> that.  But practice seems to indicate that 2 TB, or whereabout, can be
> too much.  Is this a property of a file system or we bumping into
> block device boundaries or this are just tools?

2TB is the limit for all block devices in 2.2 and 2.4 kernels.  This is
from 2^32 * 512 byte sectors.  Using LVM or MD devices will not overcome
this limitation.

There was a patch floating around which extended the block counts to
64-bit ints (Jens Axboe and/or Ben LaHaise posted it), and I think at
least part of it is in 2.5.  Even if you have 64-bit block counts,
there are other issues which pop up fairly soon - 32-bit page indexes
and other 32-bit overflows in calculations in the ext2 code.  There
is definitely a hard limit at 16TB for 4kB block ext2 filesystems,
but I suspect you will have problems at 8TB even after the 2TB block
device limit is lifted.

> BTW - mke2fs goes most of the way but gets stuck eventually when
> writing inode tables if that it is too close to 2 TB.  Yes, there
> are people who really want that much of a file system or maybe even
> more. :-)   This was not done for a sake of a record.

You could always try it on a real 64-bit machine to see if that helps.
You can concievably use 8kB blocks on an Alpha, giving you an upper
limit of 32TB for the filesystem until the ext2 extent code is
implemented (which will give us 64-bit block numbers among other things).

Cheers, Andreas
--
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert

Re: max partition size

[Alan Cox]

> that.  But practice seems to indicate that 2 TB, or whereabout, can be
> too much.  Is this a property of a file system or we bumping into
> block device boundaries or this are just tools?

Could be a bug in the drivers or request code doing writeahead
past the boundary I guess