We had problems related to partitions tables. We used gparted to create
a "gpt" partition table instead of the standard "msdos". Unfortunately
fdisk does not recognize gpt partition tables, so you need to use other
tools.
Our experience with a 8TB ext3 filesystem takes 10-12hrs for fsck &
similar times for quotacheck (depends on speed of hardware, etc). We
ended up using 4TB filesystems to reduces maintenance times.
Our local vendor built us a Supermicro/Adaptec
system with 16x1TB SATA drives. We have a 12TB
partition that they built as EXT2. When I tried
to add journaling, it took forever, and then the
system locked up. On reboot, the FS was still
EXT2, and takes hours (even empty) to fsck. Based
on the messages flying by I am also not confident
fsck rally understands a filesystem this large.