Hard Disk Monitoring

I recently bought a duplicator dock and today I tried to duplicate a WD Blue 4 TB hard drive to another WD Blue 4 TB hard drive. I have bought them at the same time as retail hard drives in February 2017. However, I was surprised that the duplicator dock refused to duplicate the hard drive because apparently the target drive was a tiny bit smaller than the source. When I checked the drives in HDS I indeed saw that the target drive was 1 MB smaller than the source (unformatted capacity 3815448 MB, number of cylinders: 7752021 and total number of sectors: 7814037168, the target has an unformatted capacity of 3815448 MB, 7752019 cylinders and 7814035055 sectors). Thus there was also a difference in cylinders, which I find somewhat strange. I have attached screen shots of the Information tab of HDS of both drives, #1 (Garfield) being the source and #2 (Fozzie Bear) being the target drive. Both drives are 100% healthy and have no reallocated or pending sectors.
I was really surprised a disk could be just a tiny bit smaller than another disk of the same type (same purchase date, same model, same firmware) and that would prevent me to duplicate the hard drive on a sector by sector basis in my duplicator dock. I have looked on the internet but have not been able to find an explanation anywhere, just someone asking a similar question, but with no good answer. Because to me you are the hard disk expert, Janos, I am wondering whether you know the reason for this difference.

Moreover, I have noticed that in HDS the same disk can sometimes have a different size. Not that in this case I do not mean a disk of the same type, but the exact same hard drive. I do not know if this is related, but I have been wondering about this for some time so I thought I would mention this here too. I have attached a screen shot of some disks where this happens taken form the offline disk selection window. Please note that the Hitachi hard drives are all 4 TB. The larger value of 5723140 MB is probably when I had the disk in a external enclosure set on BIG, but you can see that some of the other disk sizes are pretty close to each other with a small difference of a few MB, and this resembles the issue with different sizes hard drives of the same type as described above.
Thank you in advance for your reply.

Generally the disk controller where hard disks connected can cause different total addressable sectors / different total capacity.

For example if the disk is connected to internal SATA port vs. external USB port or RAID controller, it is possible that the hard disk drive appears with different capacities. This may be the reason why the same 4 TB hard disk may be detected with slightly different capacities, depending on the disk controller / connection.

But yes, it is more than weird that similar 4 TB drives used in the same connection (in the same duplicator dock) shows different capacities, especially if they have same model ID (and same firmware).

If I'm correct no Host Protected Area or Device Configuration Overlay functions used on any of the disks (which can cause different capacities by locking some part of the hard disk, usually for administrative / recovery purposes).

Personally I would try to connect the drives to internal SATA ports, exactly to verify the situation there, independently from the USB connection to verify if the USB dock is related or not.

If you have the opportunity, please use Report menu -> Send test report to developer option, would be nice to check the "raw" response of the disks, compare them and verify this difference.

The difference between those two HDD's is just 2 Sectors with 1.024MB (2 x 512Byte).

There a lot different Duplicator Docks available with different capabilities regarding how they're working. I tested several of those from Startech, Aleratech, and others.

Thank you for your responses and my apologies for my delayed reply. I had to solve more urgent technical matters first before I could collect the information you requested.

I have send you a developer's report a few minutes ago, but for completeness I am also attaching screen shots here of both hard drives when connected via eSATA to my Dell Latitude E6430 here.

The drive sizes are still different. But what is noteworthy is that one of the hard drives apparently has 4096 byte sectors, thus Advanced Format, and the other is an old fashioned 512 byte per sector drive. Very strange, because they are the same type and have the same firmware. When connected to the docking station via USB both drives were 512 byte per sector drives (see screen shots in my earlier post), which seems logical.

Best regards.

Very interesting to see the difference, especially in this case when both disks connected similarly, to same integrated controller and both drives having same firmware version too ....
So yes, we'd expect same behaviour in this case.

Really weird, I'll keep researching what could cause such difference.
Maybe is there any official answer from the manufacturer (WD)? Just curious if they may able to give some info...

Thanks for your response. I only just now noticed that you had responded. I guess I missed the notification e-mail.

It is quite telling that you do not have an explanation. Even though I really should not have invested the time for such a small issue, I just asked WD if they have an explanation. I am curious...

I will keep you informed.

Best regards.

I received a reply from WD support. They recommended me to RMA the drive. The values for the drive should be Physical Bytes per sector - 4096, Host Bytes per Sector - 512, User Sectors per Drive - 7,814,037,168. Obviously the smaller drive is faulty. They said the cause could be the drive, the setup, or how it’s being read by third party software (i.e. Hard Disk Sentinel). Of course it can then only be the drive, because I discovered the issue when trying to clone to the smaller drive in a cloning dock, which was not connected to a computer and only afterwards did I check the drive with HDS on a computer. My feeling is that it maybe has something to do with Advanced Format, because both drives should be AF, but the faulty one is not presented as such.