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    SubjectRe: [PATCH] remove 2TB block device limit
    I found the following related graph from Mr. Cahalan very informative:
    http://www.cs.uml.edu/~acahalan/linux/ext2.gif
    I just might get around to updating/expanding it.

    Padraig.

    Peter Chubb wrote:
    >>>>>>"Jeremy" == Jeremy Andrews <jeremy@kerneltrap.org> writes:
    >>>>>
    >
    > Jeremy> Peter, Out of curiousity, what then does the new filesystem
    > Jeremy> limit become, on a 64-bit system? Will all filesystems
    > Jeremy> support your changes?
    >
    > This depends on the file system.
    > See
    > http://www.gelato.unsw.edu.au/~peterc/lfs.html
    > (which I'm intending to update next week, after some testing to
    > check the new limits with my new code -- I found the 1TB limit in
    > the generic code (someone using a signed int instead of unsigned long))
    >
    > There are three different limits that apply:
    >
    > --- The physical layout on disc (e.g., ext2 uses 32-bit for block
    > numbers within a file system; thus the max size is
    > (2^32-1)*block_size; although it's theoretically possible to use
    > larger blocksizes, the current toolchain has a maximum of 4k,
    > thus the largest size of an ext[23] filesystem is ((2^32)-1)*4k
    > bytes --- around 16TB)
    >
    > It's extremely unlikely that you'd want to use a non-journalled
    > file system on such a large partition, so your best bets are
    > reiserfs, jfs or XFS. jfs and xfs work well on enormous
    > partitions on other platforms; the current version of reiserfs is
    > somewhat limited, but version 4 will allow larger file systems.
    >
    >
    > --- Limitations imposed by the partitioning scheme.
    > As far as I know, only the EFI GUID partitioning scheme uses
    > 64-bit block offsets, so under any other scheme you're limited to
    > 2^32 or 2^31 blocks per disc; some use the underlying hardware
    > sector size, some use a block size that's multiple of this.
    >
    > --- The page cache limit (which on a 32-bit system is 16TB; on a 64
    > bit system is 18 EB
    >
    >
    > Jeremy> Mind if I quote what you say on my webpage?
    >
    > Go ahead
    >
    > --
    > Peter Chubb
    > peterc@gelato.unsw.edu.au http://www.gelato.unsw.edu.au
    > -


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