Re: ELF & putting inode at the front of a file

[Matthew Dillon]

:On Mon, 6 Dec 1999, Zhihui Zhang wrote:
:> I have modified FFS filesystem code to put the disk inode at the beginning
:> of a file, i.e, the logical block #0 of each file begins with 128 bytes of
:> its disk inode and the rest of it are file data. 
:
:first question I have is, why?
:
:ron

    Good god, is he joking?  Offsetting the entire file by 128 bytes will
    break mmap() and make I/O extremely inefficient.

    Many filesystems over the years have mixed meta-data in the file data
    blocks on disk only to remove it later on when it was found to destroy
    performance.  A good example of this is the Amiga's filesystem.  The 
    Amiga's old filesystem was emminently recoverable because each data
    block had a backpointer, but it was so inefficient due to all the copying
    required that the updated filesystem removed the metadata so disk blocks
    could be DMA'd directory into the buffer.

                                        -Matt
                                        Matthew Dillon 
                                        <[EMAIL PROTECTED]>


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