On Sun, Nov 29, 2009 at 09:14:49AM -0800, John wrote: > Hi, > > I have two 3TB (hardware RAID-5) ext3 filesystems and recently added > 1TB to each. I resized each filesystem and e2fsck -f reports that both > are fine. However, when I look at the ext3 parameters with tune2fs -l > one seems to have some parameters that the other one doesn't. In > particular, one has: "Reserved GDT blocks", "Filesystem created", > "Default directory hash" and "Directory Hash Seed" while the other one > doesn't. The difference is caused on the version of e2fsprogs used to create the file systems, and to a lesser extent perhaps on the version of e2fscks you currently have installed on the systems and which you used to resize the file systems. You can check out the differences by looking at the "Filesystem features" line in dumpe2fs. It might look like this for a newer ext3 file system: Filesystem features: ext_attr resize_inode dir_index filetype sparse_super Or for a brand-new ext4 file system on a Fedora 12 or Ubuntu 9.10 system it might look like this: Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize For some features, such as dir_index, kernels have supported it for a long time, and we were late in turning it on by default. In other cases, enabling a feature may require a specific kernel version. This might not be a problem if the file system was originally created on (for example) a RHEL 3 system, and you've since upgraded to RHEL 5. So the specifics very much depend on the version of the system that you are running on, and it's hard to give general advice that is broadly applicable. > Doing some Googling, I found out that "Reserved GDT blocks" is only > important for online resizing. Since I don't do that, that's not an > issue for me. I figure that "Filesystem created" is just a timestamp > and is purely informational, so I think that's harmless if it's > missing. Yes, all of the above is accurate. > But what about "Default directory hash" and "Directory Hash Seed"? > What are the effects of either/both of those parameters missing? How > can I set/change any/all of the missing parameters? The "default directory hash" and "directory hash seed" are associated with the dir_index feature. This feature gives faster random access to a very large directories in cold cache situations. It can slow down some workloads that do readdir/stat, however, unless the application is smart enough to sort the returned results from readdir by inode number before accessing the files. Regards, - Ted _______________________________________________ Ext3-users mailing list Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
