El Capitan's Disk Utility won't format new 3 TB drives higher than 800 GB My iMac Mid.2010 running OS X EL Capitan v10.11.6 will not format any of my brand new 2 x 3 TB SATA drives and although I tried any other format like exFat, etc, it keeps making them no higher than 800 gigs.  I do connect each drive to the iMac with a "kdLinks HDD docking station" and a SATA-to-USB2 interface cable. The purpose is to use these 2 drives for Time Machine backups. What am I doing wrong? 

Update:



Also: 

2017-01-14 12:59:38.663 defaults[9465:6786462] 
The domain/default pair of (/Library/Preferences/com.apple.TimeMachine.plist, MaxSize) does not exist


Also from mount:

/dev/disk0s2 on / (hfs, local, journaled)
devfs on /dev (devfs, local, nobrowse)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
/dev/disk1s2 on /Volumes/OLDisk (hfs, local, journaled)
/dev/disk2s2 on /Volumes/SATADisk2 (hfs, local, nodev, nosuid, journaled)
Your problem is probably related to the 2.2 TB (or 2 TiB) limit. Your disks either have an MBR (instead of a PMBR) or it's a limitation of the firmware of the kdLinks HDD disk station.

Check the disks after getting their disk identifiers with disktuil list with sudo gpt -r show diskX with diskX the disk identifiers of the external disks (e.g. disk1 and disk2).

If you get an output like this:

gpt show: /dev/disk1: Suspicious MBR at sector 0
      start       size  index  contents
          0          1         MBR
          1          1         Pri GPT header
          2         32         Pri GPT table
         34          6
         40     409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
     .....


destroy the MBRs and add a proper GUID partition table.

To destroy the MBR and restore a proper GUID pt use:

diskutil umountDisk diskX
sudo dd if=/dev/zero of=/dev/diskX bs=512 count=1


Destroy the GUID partition table and create a new one:

diskutil umountDisk diskX
sudo gpt destroy diskX
sudo gpt create -f diskX


with diskX: once more the disk identifiers of your external disks.

Be sure to use the proper diskX or you may accidentally delete valid disks!



After removing the MBR you often/sometimes have to completely eject the drive (or reboot your Mac) for the changes to take effect.



Update:

With your partition data posted one can definitely say it's a 2 TiB problem:

The default size of the disk is 5,860,533,168 blocks. Your gpt output shows a size of 1,565,565,872 blocks. The difference is exactly 4,294,967,296 blocks which are 232 blocks or 2 TiB.