Rationale: mkfs defaults to reserving 5% for the root user so that critical daemons like syslogd can continue functioning in the event that the disk fills up.
Problem: Feservation for volumes >2TB means sacrificing 100GB of space for the root reserve. Syslogd does not need 100GB of space to continue functioning.
Proposal; mkfs should default to 5% or 10GB, whichever is smaller.
Patch: Behavior; mke2fs defaults to reserving 5% of the volume for the root user.
Problem: 5% of a >2TB volume is 100GB. The rationale for root reservation (syslogd, etc...) does not require 100GB. As volumes get larger, this default makes less and less sense.
Proposal; If the user does not specify their preferred reserve_ratio on the command-line (-m), use the less of 5% or MAX_RSRV_SIZE. I propose 10GiB.
Patch: Attached or http://capsid.brandeis.edu/~elrad/e2fsprog.gitdiff
Tested on RH5 with a 12TB volume:
# /root/e2fsprogs/misc/mke2fs -T ext4 -L scratch /dev/sdd1
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
732422144 inodes, 2929671159 blocks
2621440 blocks (0.09%) reserved for the super user