status of dir_index in 2.4 kernels ?

[Jakob Curdes]

Ok, I try to summarize what I gathered from this and the earlier  thread 
to help other "htree newbies"
(Please correct my statements if necessary):

- To use htree enabled ext - Filesystems in 2.4 kernels, you need
 a) a htree enabled kernel; patch against 2.4.21 can be found at

       http://thunk.org/tytso/linux/extfs-2.4-update/

Curiously enough, I colud not apply this patch against a clean 2.4.27 
tree - is there anything special to be aware of ??

b) the current e2fsprogs which you can get from

    http://e2fsprogs.sourceforge.net/

c) you have to enable dir_index on the filesystem with
     
<>    # umount /dev/xyz
    # tune2fs -O dir_index /dev/xyz
    # e2fsck -fD /dev/xyz
    # mount /dev/xyz

d) The performance of the htree indexed filesystem depends on the usage 
by the userspace programs; if they open all files in a directory after 
gaining directory information with readdir() the performance is worse 
than with a vanilla ext3 fs, at least if we have many files in that 
directory [as it is the case with maildir structures].  This can be 
cured by an additional userspace library which can be found in the message

https://www.redhat.com/archives/ext3-users/2004-September/msg00025.html

e) One question remains open : Is the htree feature in its current state 
considered stable enough to be used in production systems ?
I read some reports on filesystem corruption, but most of these applied 
to older versions of htree. Are there differences between the 2.6 
implementation and the 2.4 backport ?


Thank you for comments,

Jakob Curdes




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