[CentOS] 3TB External USB Drive isn't recognized

Tue Aug 13 15:13:26 UTC 2013
Lamar Owen <lowen at pari.edu>

On 08/12/2013 12:21 PM, John R Pierce wrote:
> ... and MBR disks have an absolute maximum size of 2TB 

Actually, no.  The size of disk usable in an MBR partitioning scheme is 
dependent upon the disk's block size; with 4k blocks MBR can (and does) 
go above 2TB.  We actually have a pair of Western Digital 3TB externals 
that are NTFS-formatted and MBR partitioned.  Yes, this is non-standard 
and breaks the 'letter' of the MBR specs, but, it works fine on Windows, 
which is the target audience.  The Mac-formatted Studio drives are GPT 
partitioned (and cost more).  The Linux HFS and HFS+ filesystem drivers 
don't like the 3TB HFS+ formatted WD Studio 3TB I have here, either......

see: http://forums.anandtech.com/archive/index.php/t-2174705.html and 
the comment by Mark R down the page a bit.  Seagate and WD both do this 
with external 3TB drives meant for PCs.

WD does something very similar for their MyBookLive models; these units 
are the network-attached ones, and 3TB single-drive and 6TB dual-drive 
units are common.  The NAS embedded OS is Linux, and the main data 
partition is formatted 64k-blocksize ext4:

(This is on a 1TB model....)

LOMBL1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/md0              1.9G  541M  1.3G  30% /
tmpfs                 5.0M     0  5.0M   0% /lib/init/rw
udev                   10M  6.7M  3.4M  67% /dev
tmpfs                 5.0M     0  5.0M   0% /dev/shm
tmpfs                 100M   10M   90M  10% /tmp
ramlog-tmpfs           20M  3.4M   17M  17% /var/log
/dev/sda4             924G  922G  2.5G 100% /DataVolume
LOMBL1:~# tune2fs -l /dev/sda4
tune2fs 1.41.12 (17-May-2010)
Filesystem volume name:   <none>
Last mounted on:          /CacheVolume
Filesystem UUID:          2631203b-3cb5-4f63-b9ae-12fed7e5d0bd
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index 
filetype needs_recovery extent flex_bg sparse_super large_file huge_file 
uninit_bg dir_nlink extra_isize
Filesystem flags:         unsigned_directory_hash
Default mount options:    (none)
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              15144960
Block count:              15191355
Reserved block count:     0
Free blocks:              892140
Free inodes:              14734611
First block:              0
Block size:               65536
Fragment size:            65536
Reserved GDT blocks:      32
Blocks per group:         65528
Fragments per group:      65528
Inodes per group:         65280
Inode blocks per group:   255
Flex block group size:    16
Filesystem created:       Thu Apr  7 19:26:05 2011
Last mount time:          Tue Jun  4 16:02:59 2013
Last write time:          Tue Jun  4 16:02:59 2013
Mount count:              15
Maximum mount count:      29
Last checked:             Thu Apr  7 19:26:05 2011
Check interval:           15552000 (6 months)
Next check after:         Tue Oct  4 19:26:05 2011
Lifetime writes:          1173 GB
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:              256
Required extra isize:     28
Desired extra isize:      28
Journal inode:            8
Default directory hash:   half_md4
Directory Hash Seed:      4a2c0236-2d62-4779-bb5b-950094980616
Journal backup:           inode blocks
LOMBL1:~# parted /dev/sda print
Model: ATA WDC WD10EACS-00Z (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system Name                  Flags
  3      15.7MB  528MB   513MB   linux-swap(v1)  primary
  1      528MB   2576MB  2048MB  ext3 primary               raid
  2      2576MB  4624MB  2048MB  ext3 primary               raid
  4      4624MB  1000GB  996GB   ext4            Microsoft basic data

LOMBL1:~# cat /etc/debian_version
LOMBL1:~# uname -a
Linux LOMBL1 #1 Thu May 17 13:32:51 PDT 2012 ppc 

Oh, but 64k blocksize ext4 is NOT supported on almost all PC linux 
distributions, including CentOS.....  At least it's not a funky MBR 
format, and GPT is used.... And yet the MyBookLive runs Debian 
5.0.4/PPC...... Go figure.  For more info on the MyBookLive from a linux 
point of view, see http://mybookworld.wikidot.com/ (it's a fun box to 
play with, and much more robust than the previous 'World Edition' drives).

CentOS works fine with the SMB shares the MBL exports, and I'm using one 
right for backups.