I had recently to import a LVM previously created on a SLES9 (in fact i scratched the SLES that was installed on a separate disk). Of course lvm is lvm so i had direct access to the datas sitting in my logical volume. Everything was fine except that i was asked in the same time to extend the filesystem (a new disk was added in the volume group). Because i told the customer that it was easy with resize2fs (now supporting online extend on el5 , while you needed ext2online on el3 and el4), i decided to do it directly after my migration (understand after having scratched and replaced the SLES). But i had a surprise when trying to extend the filesystem : it didn't work !
resize2fs answered me : 'resize2fs: Operation not permitted While trying to add group' .. and /var/log/messages told me : 'No reserved GDT blocks' ... hmm, what does that mean ? inspecting the filesystem with `tune2fs -l` showed me that the ext3 filesystem created on SLES was lacking an important feature (already present for a while on RHEL/CentOS/others ...) : the resize_inode function was missing in the Filesystem features .. damn ... `man tune2fs` was not a great help because it seems that it was not possible to add the missing feature .. so i decided to use resize2fs offline (and of course it worked) ...
But i was frustrated (and the customer too) because i told him that it was just easy to extend a lvm/filesystem on-the-fly [TM] .. so, while extending the filesystem unmounted, i decided to google a bit and i found an interesting thing about a patch being added by redhat in tune2fs that allows to add the resize_inode feature !
`rpm -q --changelog e2fsprogs|grep resize_inode` returned me : - enable tune2fs to set and clear feature resize_inode (#167816)
I tested this (on a separate machine) and it worked .. always interesting to know if you import an ext3 filesystem from a system that didn't use the resize_inode ext3 feature (check the defaults that mkfs.ext3 use on a CentOS/RHEL/Fedora in /etc/mke2fs.conf)