ext4 partition works but fdisk shows no valid partition table

ext4 partition works but fdisk shows no valid partition table

I have a 1TB disk with a single ext4 partition.
here's some output of parted print all command
Model: ATA Hitachi HDS72101 (scsi)
Disk /dev/sdb: 1000GB
Sector size (logical/physical): 512B/4096B
Partition Table: loop

Number  Start  End     Size    File system  Flags
 1      0.00B  1000GB  1000GB  ext4
However fdisk reports that there is no valid partition
Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

Disk /dev/sdb doesn't contain a valid partition table
testdisk /dev/sdb reports
Disk /dev/sdb - 1000 GB / 931 GiB - CHS 121601 255 63
Current partition structure:
     Partition                  Start        End    Size in sectors

Partition sector doesn't have the endmark 0xAA55
then testdisk deepscan finds
Linux           0   0  1 121601  80 63 1953525168 [storage]
When I try to add this partition in testdisk it doesn't do anything and just exits to screen showing no partitions.
this is my secondary data drive that I'm currently using daily. I have data on it that I'd rather not nuke. I'm not sure if I should be concerned about this or if I should not worry about it. The disk works but I don't know if it's a failure waiting to happen.
Question: Where to go from here if I want to make sure the disk is setup optimally?