Re: xfs filesystems greater than 1 TB with inode size = 256?

[Steve Lord <lord@xxxxxxx>]

Iustin Pop wrote:
> On Tue, Dec 23, 2003 at 01:11:21PM -0600, Steve Lord wrote:
>
> > However, things will behave a little better with the larger
> > inode size.
>
>
> Hello,
>                                                                                                                                                     
> Could you please explain why and maybe also give some explanations about
> how this affects performance on smaller filesystems (<1TB)? I didn't
> find anywhere informations related to inode size impact, and I wonder if
> tuning it makes a difference.
>                                                                                                                                                     
> Thanks,
> Iustin Pop

Because it (larger inode size) allows inodes to be distributed over the
whole filesystem, and hence there is more chance they will be closer to
the file data. This all comes from the fact that xfs dynamically
allocates inodes when needed instead of creating them at mkfs time, the
location of an inode is encoded in the inode number. Making the inode
size larged means that you need less bits to index into the block 
containing the inodes, therefore have more bits to use for the disk
address.

Larger inodes mean you can put more exents or directory contents into
the inode, so a larger percentage of inodes in the system will not have
out of line metadata. So larger inodes can make things faster in some
cases. They can also make things slower since you have to read/write
more blocks to cope with the same number of inodes. So basically it is
a balancing act, and it depends on your application.

Steve