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# What is a Petabyte?

R. Kayne
R. Kayne

In the world of ever-growing data capacity, a petabyte represents the frontier just ahead of the terabyte, which itself runs just ahead of the gigabyte. In other words, 1,024 gigabytes is one terabyte, and 1,024 terabytes is one petabyte. To put this in perspective, a petabyte is about one million gigabytes (1,048,576).

In the late 1980s, a large hard disk was considered 80 megabytes. Today, that amount of space doesn’t even hold a current Windows operating system without butting up against storage limits. Robust programs, music files, digital versatile discs (DVDs), streaming video and high-resolution graphics have all become memory-hungry beasts devouring real estate bit by byte. It would have been unthinkable in the 1980s that the home computer would one day require tens and even hundreds of gigabytes to store data. Though the petabyte still lies beyond the territory of the terabyte, who can say where the home computer will be in another two decades?

It’s a humbling thought that the mighty petabyte stores individual bits. It takes eight bits to make a byte, which represents a single character. The word “bit” for example, takes 24 bits to spell, or three bytes.

Put 1,024 bytes together and you have a kilobyte. Take the same amount of kilobytes (1,024) and you’ve built a megabyte; 1,024 megabytes and you have a gigabyte – and so on to get a terabyte, and finally, a petabyte. So how many bits are in a petabyte? A staggering 9,007,199,254,740,990!

For the average person, the number crunching gets a little hairy when moving into the territory of the petabyte, but it doesn’t stop there. Beyond the petabyte are the exabyte, zettabyte and yottabyte. While some may still be getting used to the idea that 1,024 megabytes equals one gigabyte, we’re fast coming upon the time when people will be referring to having “half a terabyte” storage, rather than 500 gigabytes. For now, however, the petabyte is safely relegated to university-owned supercomputers like those of Indiana University, The European Organization for Nuclear Research (CERN), and IBM’s Global Services, among others. We can only hope that by the time the home user is buying storage capacity by the petabyte, defragmentation programs have kept pace.

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anon929729

Anyway, I really enjoyed reading the above article, and after the second reading, I noticed this: “We’re fast coming upon the time when people will be referring to having “half a terabyte” storage, rather than 500 gigabytes.”

That is so very, very true. I have already seen laptops advertised as having a 1/2 a terabyte HDD. It’s as if gigabyte seems like a "low" word now. I certainly think and talk in terabytes now for mass storage, and that’s after years of gigabyte talk.

Will we as home users, ever need a petrabyte at home? That’s 1,000 terabytes, folks (forget about the 1024 v 1000 for now).

Well, the reason why terabytes are in my vocabulary is because of video. Obviously, if I just had word docs and spreadsheets and a few mp3s, then gigabytes would still seem massive to me.

But video files changed the game for me, and don’t forget if you have a master external HDD to back up everything you have, then this master” should be exceptionally big to accommodate all your stuff. My current master backup HDDs are a single 3TB HDD and two single 500GB HDD. So that’s 4 TB total (And the HDDs are not full). In a couple of years, I reckon I may need a 5- 7 TB master. We are way, way, way behind 1000 TB. In fact, not even approaching 15TB. So what awaits us in the future to want or need 1PB at home?

anon929721

@mumford68 Post 9: As simply as possible, the computer industry

(Microsoft Windows Operating System) thinks, reports and see am HDD in binary terms -- therefore 1000 as you I think of 1000 is actually 1024 to your computer.

Human Beings and the companies that make HDDs think and design in decimal. Therefore 1000 = 1000. So, when you buy a 160 GB HDD your computer (Windows OS) looks as sees the drive in 1024 (binary). But, because the HDD makers are working in 1000, it means you are "missing" 24 in every 1000. If the HDD manufacturers were working in binary, then they would say for every 1000 we really mean 925. So 925 is your helper here. You will fall in love with it.

Here is the formula: 0.925 multiplied by anything the manufacturers are claiming will always give you a closer value to what your Windows OS will report and see. Example: 0.925 x 160GB = 148 GB. Of course, nothing is really missing or disappeared; 148 is the amount of space you will be reported as having on a Windows OS. And by the way, all HDD manufacturers do this.

I for one, have long believed that both parties should agree on one standard system. Imagine a carpenter working in inches and the wood supplier working in feet and there is no conversion chart. “Can I have 7 inches of Chillian Brown Alpine Dark Wood please?” And just to cause trouble, if you put that exact same drive via USB onto some Linux OS, it reports in 1000, so you would see a reported 160GB Available. I don’t know about the Mac OS. Maybe someone else could tell us here how the Mac OS sees and reports.

Remember the 0.925 formula rule. -- Thomas J

mumford68

I am a bit more confused as I don't quite understand what you mean by "security device" and even if this is so, why is it that the larger the HD the more space you are "missing".

I have a 160GB HD and right after formatting it shows about (I think it was) 150GB total space that is a 10GB difference (does not make sense even giving a large reserved portion of 1GB for WinXP files, boot information etc. and whereas your HD of 2TB is "missing" around .19TB or a whopping 190GB of "missing" space.

So if a person in the future gets a 10TB drive they will only be able to use 9TB of it. It's a little confusing to me.

anon166188

This is really interesting, but I feel like I'm missing something. If I go to a Word document and select "word count", and it reports that the document has 5,330 characters (not counting spaces), then it would stand to reason that 5,330 character would equal 5,330 bytes, but when I look at the size of the saved document, the "size" is listed as either 162 bytes, or "size on disc" is listed as 4,096.

I would have actually thought that it would have been more than the 5,330 bytes with any background formatting or font characters that are hidden. Why the discrepancy?

anon150800

@mumford68: The reason behind the "missing space" on the hard drive is because the drive manufacturers install security devices and other data on the hard drive that cannot be erased. I just bought a 2 TB external hard drive, and when I opened up "My Computer," it said 1,81 TB free. It's just from the system files on the drive, etc.

anon95482

Actually, the 1024 count is a binary byte, represented by a different set of measures. Kibi, mibi, gibi, etc. It's an IEEE standard that most IT professionals don't know about.

True metric measurements are still base 10.

anon65428

I'm not a computer geek, but even i understand that computers run on binary, hence the seemingly strange, at least according to the comments I've seen on this page, numbers for storage. Everything is based on powers of two, hence a kilobyte being 1024 bytes, etc., etc., instead of 1000.

mumford68

I wonder if this could be a little dumbed down for myself. I understand it takes 8 bits to make a byte but why is it that a newly formatted hard disk drive has considerably less space than the drive space rating of the drive?

anon59123

Did you know that the USPS stores over 2 petabytes of data online? That's equal to 4,000 years worth of MP3 songs!

habura

Anon33274 - Kilo does stand for 1,000 in the decimal world, but in the binary world, a kilo is 1,024 (2 to the 10th power). I agree that a kilo *should* be a kilo, but that's how the term developed with respect to computing. What can you do? It's not going to change just because a few of us want to hold true to the definition of a kilo.

anon33274

The drive manufacturers have it right. One kilobyte = 1000 bytes not 1024. One megabyte = 1,000,000 bytes not 1024 x 1024. Follow the same pattern for gigabyte, terabyte, and petabyte!

Stop spreading the myth created when someone looked at 1024 bytes and said "its close enough to 1000 so lets call it a kilobyte".