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Why some unaccesible space is reserved in a storage?

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Why some space is reserved in a HDD? I have a 320 GB HDD and my system only shows 298.01 GB of it. I couldn't recover that space even with a clean format of the HDD. Where that 21.91 GB goes then? The same is with my pendrive. Why is that?
 
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Read something about this here: http://www.howtogeek.com/123268/windows-hard-drive-wrong-capacity/

Some space is reserved by Windows, some is just not there (advertised were 320GB, but there isn't this much space anywhere). Check for Manufacturer recovery partitions - but there isn't much you can do about this ;-)

Sample calculation:

Advertised: 320,00 GB
Physically available space: 298,023 GB
 

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There's no lost space. HDD manufacturers quote capacity in base 10, while Windows reports it more correctly in base 2 so it appears smaller. It's just a little ruse by the HDD manufacturers to make their drives seem bigger.
 
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There's no lost space. HDD manufacturers quote capacity in base 10, while Windows reports it more correctly in base 2 so it appears smaller. It's just a little ruse by the HDD manufacturers to make their drives seem bigger.
yep, because the difference of counting storage and your hdd may have little bit lower than 320gb
 
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yep, because the difference of counting storage and your hdd may have little bit lower than 320gb

Yep - exactly 21,977 GB less.

Which answers the initial question:

Where that 21.91 GB goes then?
 
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I have a 320 GB HDD and my system only shows 298.01 GB of it.
It is because HDD manufacturers use GB (1GB = 1000000000 / $3B9ACA00 bytes) and Windows GiB (1GB = 1073741824, $40000000 bytes).

That's why.
 

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Also space is "reserved" in so much as when bad sectors are fixed in many cases they are not, they are moved and bypassed, there must always be a place to move them.
 

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Also space is "reserved" in so much as when bad sectors are fixed in many cases they are not, they are moved and bypassed, there must always be a place to move them.
I think it's also important to clarify that that this doesn't detract from the reported "full" capacity of the drive, as these are extra sectors, only visible to the disc controller. Only once all the extra sectors are used up would you notice a drop in capacity, by which point the drive should be replaced anyway.
 
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Can I calculate this "pseudo space" in a fixed percentage? I mean, what about 500 GB and 1 TB drives? Is this scenerio same for SSDs?
 

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For SSDs it depends how the manufacturer specifies the capacity. You can be sure that if they specify them in powers of 2, such as 128, 256, 512, 1024 etc then they are using base 2. If it's an odd capacity then you need to check the small print.

The percentage is always the same. So check what the difference is for your drive in percentage and apply that to other sizes, except where it's already a power of 2 like I explained.

Note that formatting always reduces the available capacity of any drive.
 
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Much like folders in a filing cabinet take up total space for papers, formatting takes up physical space to number the locations in the drive. Also there is a partition and MFT (master file table) that is created amd is always large enough to hold the file information for every file the drive could hold and metadata. There will also be some lost to sector size for the format VS native sector size, and as well any files tgat don't match sector sizes will be stored using two sectors and one may be almost empty.

The only difference between the manufacturers reported size and windows reported size is caused by the partition and formatting that is required by your operating system to efficiently and reliably hold data.
Storage is cheap though.
 
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Can I calculate this "pseudo space" in a fixed percentage?

Just look at the article I've posted, they perform a sample calculation. For HDDs: (Advertised Storage in Bytes) / (1024*1024*1024) = Actual Space

SSD are somewhat odd. They have a certain amount of space reserved in case to many sectors die because they hit the maximum of R/W cycles. Other SSDs use a dedicated swap partition, others do both. You never know for sure, but you can ask the manufacturer.
 
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The difference is usually around 7.37% give or take 0.1%. SSDs are a little different. SSDs physically have all the space but some of it is reserved for over-provisioning (magic SSD stuff). 256GB and 240GB SSDs physically have 256 gibibytes but will only have 238GiB(256GB ~7% over-provisioning) or 223GiB(240GB ~12.6% over-provisioning) usable.
 
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Deleting a post to which another post refers isn't fixing anything. I'm a forum mod/pu myself (german forum) and it is really annoying when people do this. The flow of the conversation is disturbed in an odd way. :rolleyes:
 
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Metric defines it as:
1KB = 1000 bytes
1MB = 1000 KB
1GB = 1000MB
1TB = 1000GB
etc.

JEDEC uses a binary representation (which is how computers count it,) where:
1KB = 1024 bytes
1MB = 1024 KB
1GB = 1024 MB
1TB = 1024 GB
etc.

By the time you get to a terabyte, the metric representation looks something like 1,000,000,000,000 where the binary representation would look something like 1,099,511,627,776. So from 1TB that's ~92.67GB (or GiB if you will) that they essentially swindled you out of.

Now consider someone like me who has 4x1TB drives. In RAID-5 I only effectively see 2654.72GB of storage because of it instead of 3000GB (granted in addition to how it is counted, there is more space that is used for partitioning and file systems and such.)
 

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Can I calculate this "pseudo space" in a fixed percentage? I mean, what about 500 GB and 1 TB drives? Is this scenerio same for SSDs?

Much like qubit said, for powers of 2, yes. But lately you are seeing SSD's with 120GB or 240 GB capacity, etc. They are automatically reserving the extra space, so a 240GB SSD now has the same storage space as one listed as 256. They've just set aside 16GB for wear levelling, etc.
 
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Yeah, there is a slight difference between MS and HDD vendors as to what is included and how it's calculated: Bit&Bytes. :)

In the end the end I think it all boils down to marketing really.......my 2c.

Edit:
**In a nutshell 2 methods of calculation are used, Vendors calculate physical space, and Windows calculates the amount of binary data that can fit on that space.

It's quite retarded when u think about it... But that's computer science for you. lol
 
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Can I calculate this "pseudo space" in a fixed percentage? I mean, what about 500 GB and 1 TB drives? Is this scenerio same for SSDs?
My WD 1TB drive gives me 906 gb of usable space. which comes out to about 90.6 percent of the advertised storage capacity. if we apply that to your 320gb drive then it comes out to about 289gb, however you have 298gb of space available. So I would assume you lose a slightly larger percentage of space as you increase the hard drive capacity.
 
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I should amend what I said. The difference is around 7.37% when using gigabytes as the basis. It changes to around 9.95% (I think, somewhere around there) when using terabytes.
 
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It is because HDD manufacturers use GB (1GB = 1000000000 / $3B9ACA00 bytes) and Windows GiB (1GB = 1073741824, $40000000 bytes).

That's why.
Ugh, I kinda forgot how to convert hexadecimal to decimal. So could you please translate that? And why is there a dollar sign for?
 
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Ugh, I kinda forgot how to convert hexadecimal to decimal.
It's easy, image below:



If you meet an A-F value, just pick 10-15 instead...

So could you please translate that?
I meant: 1GB = decimal / hexadecimal in bytes.

And why is there a dollar sign for?
It is for you to know that is a hexadecimal number, other people use 0xFFFFFFFF for example.
 
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Stick to the topic and not each other.
 
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Why some space is reserved in a HDD? I have a 320 GB HDD and my system only shows 298.01 GB of it. I couldn't recover that space even with a clean format of the HDD. Where that 21.91 GB goes then? The same is with my pendrive. Why is that?

Wow, nobody really spelled it out clearly for OP. HDD manufs talk in 1000 (shady marketing) while everyone else uses 1024.

320,000,000,000 / (1024^3) = 298.02GB

If you really need 320GB then you need to find:

320*(1024^3) = 343,597,383,680 = "343.6GB" drive
 
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