Why is quotacheck so slow?

Hi,

I am preparing a new fileserver with quota support. I wonder if I am
doing sowmthing wrong, because quotacheck takes more than 15 minutes on
an empty filesystem. OK, it’s 2 TB in size, but no data on it. Is this
normal behaviour? I’d expect quotacheck to not check anything at all
under these circumstances…?

mkfs.ext3 /dev/mapper/raid6-home

mke2fs 1.40.8 (13-Mar-2008)
Warning: 256-byte inodes not usable on older systems
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
134217728 inodes, 536870912 blocks
26843545 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
16384 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632,
2654208,
4096000, 7962624, 11239424, 20480000, 23887872, 71663616,
78675968,
102400000, 214990848, 512000000

Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 22 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.

mount /dev/mapper/raid6-home /home

df /home

Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/raid6-home
2113787824 202920 2006210724 1% /home

time quotacheck /home

real 16m25.759s
user 0m6.588s
sys 0m37.042s

disks are heavily active during quotacheck… but what do they do…?