Reiserfs speed (Was: Re: [gentoo-user] Re: Size of portage tree)

[Richard Fish]

Harry Putnam wrote:

>I am using reiserfs but only on trial basis.  I've noticed what
>appears to be quite a large increase in time needed for fs intensive
>things like du or rm -rf as compared to ext3 but I've done no real
>comparison testing.
>
>Have you noticed that too?
>
>

This is normal, and it's a feature.  Reiserfs uses hash values to speed 
the lookup of single files, and as a result the readdir() system call in 
reiserfs (which is what find, rm -rf, and du use to walk a directory 
tree) returns file names in order of their hash value, which probably 
does not match the order of the files on disk.  On the other hand, ext3 
readdir() returns files in inode order.  This means the disk will 
typically have to do more seeking for these operations on reiserfs than 
ext3, which returns file names in inode order.  Actually, you can see 
similar performance differences between ext3 filesystems formatted with 
"-O dir_index" and those without.

You can 'fix' this by tar'ing, reformatting, and restoring the 
filesystem, which will have the effect of ordering files on disk 
according to their hash value. 

Cheers,
-Richard
-- 
gentoo-user@g.o mailing list