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Lost HDD capacity on new drive

Last response: in Storage
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August 3, 2010 7:34:28 AM

I have a new 1TB SATA drive installed. I installed it and formatted it and it was showing the full 1TB.

Using Win7 Disk Manager I created numerous partitions and removed them.

At one stage I had a 20GB partition and a 980GB partition on it. I decided to shrink the 980GB partition by 40GB to 940GB so I could expand the 20GB partition to 60GB. Then I ran into a problem.

Firstly, the option to expand the 20GB partition was greyed out, so I deleted both and went to start again. Only thing is my whole HDD drive is now only showing a 930GB capacity, even when I remove all volumes.

I've tried re-formatting and creating and removing volumes. Then I disabled the driver and the HDD, removed the driver and re-installed it all again but it's still showing the reduced capacity. The worrying thing it is even showing the 930GB capacity in the RAID devices when my pc boots up before windows kicks in.

I'm not an expert and I figure it must be something simple because surely you can't just wipe out your drive's capacity like that.

What can I do to restore my HDD's capacity.

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a b G Storage
August 3, 2010 8:50:39 AM

I don't know how you got that 1TB drive to be full when you first used it. No HDD are detected by OS as their full rated capacity. My WD 1TB is 931GB. That is quite normal, nothing to worry about there.

There's a catch in HDD sizes. HDD manufacturers rate their HDD with 1000KB = 1MB method. While OS recognizes the HDD as 1024KB = 1MB. So there is a loss in size. You can do the calculations.

1TB = 1000 GB = 1,000,000MB = 1,000,000,000KB (this is for HDD manufacturers)

But for OS:

1,000,000,000KB = 976562.5MB = 953GB approx!

Cut out some part for file allocation and boot sector info. I dont think they are added into the OS detection. You get what you have now.

Hope this helps.
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August 3, 2010 9:07:44 AM

Ok, that makes sense - maybe I just didn't realise it was already 930GB and just freaked out when I did finally notice.
Cheers
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a b G Storage
August 3, 2010 5:10:05 PM

Yeah, the unit of measure is misleading. That's why if you read the fine print on retail hard drives you'll see a disclaimer that says 1GB is defined as 1,000,000,000 bytes (which as hell_storm pointed out is not entirely true).

The units are actually GB and GiB. Read more here. As hard drive capacities have increased, the disparity between GB and GiB becomes even greater. Back in the old days, no one cared that their 40GB hard drive was seen in Windows as 37.2GiB.

The easy way to convert GB to GiB is the following equation:

#GB/1.024³ = #GiB

So for a terabyte drive (1000GB): 1000GB/1.024³ = 931.3GiB

A 500GB drive is 465.7GiB
A 320GB drive is 298.0GiB

so on and so forth.

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August 14, 2010 3:03:24 AM

Best answer selected by mullenmj.
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a b G Storage
August 14, 2010 4:53:35 AM

hell_storm2004 said:
I don't know how you got that 1TB drive to be full when you first used it. No HDD are detected by OS as their full rated capacity. My WD 1TB is 931GB. That is quite normal, nothing to worry about there.

There's a catch in HDD sizes. HDD manufacturers rate their HDD with 1000KB = 1MB method. While OS recognizes the HDD as 1024KB = 1MB. So there is a loss in size. You can do the calculations.

1TB = 1000 GB = 1,000,000MB = 1,000,000,000KB (this is for HDD manufacturers)

But for OS:

1,000,000,000KB = 976562.5MB = 953GB approx!

Cut out some part for file allocation and boot sector info. I dont think they are added into the OS detection. You get what you have now.

Hope this helps.


Actually, you missed a step. For the HDD manufacturers, 1 TB = 1,000,000,000,000 bytes.

To the OS, 1 kB = 1024 bytes, so 1,000,000,000,000 bytes = 976,562,500 kB.

1MB = 1024kB (again, according to the OS), so 976,562,500 kB = 953,674 MB.

1GB to the OS = 1024MB, so 953,674 MB = 931.32 GB, which is exactly how much you're seeing.
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