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Re: Inode/Blocksize questions

On Mon, 29 Apr 2002, Michael Renner wrote:
> I'm going to build a maildir-based mailserver with a ~56 gb
> mail-partition. What blocksize/bytes-per-inode/number of inodes should i
> use (i don't want to ran out of inodes and don't want to sacrifice too
> much space for filefragments)?
> Is there a drawback when lowering the blocksize/increasing the number of
> inodes (except the maximum filesystem size)?
> The inodes used by a file is always filesize divided by the blocksize
> rounded up to the next absolute value, isn't it?
> best regards,
> Michael Renner


A smaller blocksize will generally result in slower performance.  On the
other hand, you'll lose less space per file with a smaller blocksize.
With default options, the number of inodes mke2fs creates is 1 per 8kB of
disk space.

Looking at my mailbox, my average message size is ~9kB.  For me, the
default number of inodes should be just about right (since each message
uses one inode, and including some extra inodes for directories and other

Inodes used by a file is always one (unless you have multiple links
pointing to the file).  The blocks used by a file is:
    floor(filesize / blocksize) + 1
floor(n) is the greatest integer less than or equal to n (or, n is rounded
down).  Assuming file sizes are randomly distributed, on average (mean)
you'll lose 1/2 block per file.

If you're really worried about space efficiency, then as bad as it may be
to say on the ext3-users list, you may want to consider reiserfs - it
usually benchmarks faster on small files (where "small" is under 15kB, I
think), and is more space-efficient then ext2/3, if you enable tail

      -Matt Stegman

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