RHEL5 ext3 vs ext4

Hi All,

I'm looking for some timing figures regarding fsck and ext3

I've been asked to add another 6.5TB to an existing 5.8TB LV.

Before I tell the customer go away and multiply, I'd like to find out how long it would take to FSCK a 12TB ext3 filesystem and if there are any LVM issues before recommending recreating the filesystem using ext4. (which will create at least a days downtime to restore the data), where as sticking with ext3, no downtime at all. (until the next reboot)

~~~
[root@host]# df -h /u[1-2]00
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/DBGroup27-Data27
5.8T 4.8T 767G 87% /u100
/dev/mapper/DBGroup27-Backup27
985G 545G 390G 59% /u200

[root@host]# pvs
PV VG Fmt Attr PSize PFree
/dev/emcpowera1 DBGroup27 lvm2 a-- 499.99G 0
/dev/emcpowerbk1 DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbl DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbm DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbn DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbo DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbp DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbq DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbr DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbs DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbt DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbu DBGroup27 lvm2 a-- 500.00G 0
/dev/emcpowerbv DBGroup38 lvm2 a-- 500.00G 0
/dev/emcpowerbw DBGroup38 lvm2 a-- 500.00G 0
/dev/emcpowerbx DBGroup38 lvm2 a-- 500.00G 0
/dev/emcpowerby DBGroup38 lvm2 a-- 500.00G 0
/dev/emcpowerbz DBGroup38 lvm2 a-- 500.00G 0
/dev/emcpowerq1 DBGroup27 lvm2 a-- 499.99G 0
/dev/emcpowerr1 DBGroup27 lvm2 a-- 499.99G 0
/dev/emcpowers1 DBGroup38 lvm2 a-- 499.99G 0
/dev/emcpowert1 DBGroup38 lvm2 a-- 499.99G 0
/dev/sda2 VolGroup00 lvm2 a-- 135.62G 0
/dev/sdb1 VolGroup00 lvm2 a-- 836.59G 0
[root@host]# vgs
VG #PV #LV #SN Attr VSize VFree
DBGroup27 14 2 0 wz--n- 6.84T 0
DBGroup38 7 2 0 wz--n- 3.42T 0
VolGroup00 2 8 0 wz--n- 972.22G 0
[root@host]#
~~~

Regards
Jonathan