[Discuss] Experience Formatting Ext4 volumes beyond the 16TB limit

[sgoldman at MIT.EDU (Stephen B Goldman)]

Hello Blu,
                Does anyone have experience formatting Ext4 volumes beyond the 16TB limt ?   Creating a storage server using LVM's and I which to create a 85 TB volume.  I found a method to update the utilities . Seeking feedback from others who have had a need to do this before .

Running - rhel 6.4
Linux  2.6.32-431.el6.x86_64 #1 SMP Sun Nov 10 22:19:54 EST 2013 x86_64 x86_64 x86_64 GNU/Linux

Thanks,
Stephen





Formatting Ext4 volumes beyond the 16TB limit
Article98
CreatedFebruary 22, 2013
Authorcaurelio
Ratingn/a

All filesystems have limits, and the Ext family is no exception. Using your standard 4KiB block size, the 32-bit Ext3 has a well-known limit of 16TB for a volume. With the advance of storage mediums and greater availability of increased capacity, Ext4 was developed to overcome this limitation. Ext4 will now support volumes up to 1 exbibyte (EB).

This is a fantastic, improvement, but what happens when you actually go to format one of these volumes? If your system is running with some of the older fs tools (like Debian Squeeze), then you will probably encounter this scenario when trying to format a large volume (let's say we have a 19TB partition at /dev/vg0/lv_data for this example).
# mkfs -t ext4 /dev/vg0/lv_data
mke2fs 1.42.7 (21-Jan-2013)
mkfs.ext4: Size of device (0x131a47800 blocks) /dev/vg0/lv_data too big to be expressed in 32 bits using a blocksize of 4096.

Although the Ext4 filesystem has been updated to support 64-bit volumes, the tools may not be. The solution here is to grab the latest version of the e2fsprogs utilities and build them yourself.

Stephen Goldman
Systems Administrator
Massachusetts Institute of Technology
Department of Biology
31 Ames Street 68-211
Cambridge, Ma 02139
sgoldman at mit.edu -617-452-2595