Linked by Thom Holwerda on Fri 19th Oct 2012 20:07 UTC
Windows Interesting little tidbit from the Reddit AMA session with Microsoft's Surface team. One Redditor wondered just how much disk space Windows RT takes up - in other words, if you buy the 32GB Surface RT tablet, how much space is left for your stuff? It turns out that while Windows 8 RT is considerably smaller than its Windows 7 x86 predecessor, it's still huge by mobile standards.
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RE: Not quite true
by tanzam75 on Sat 20th Oct 2012 01:22 UTC in reply to "Not quite true"
tanzam75
Member since:
2011-05-19

And it's not even 12 GB. It's actually 9.8 GiB.

I can't believe nobody has pointed this out yet.

What Microsoft actually said on that Reddit thread was that "After the OS, OfficeRT and a bunch of apps, you will still have more that 20GB." Thus, they did not say that disk usage was 12 GB. They said that free space was 20 GB.

Ah, but how did he get that free space figure? Probably in Windows Explorer -- which reports free disk space in binary gibibytes, even though it uses the "GB" abbreviation. Yet flash memory is sold using decimal gigabytes. My "128 GB" SSD is reported as "119 GB [= GiB]" in Windows Explorer.

A 32 GB flash drive = 29.8 GiB. If you have "more than 20 [GiB]" of free space remaining, then that means the entire running system takes up 9.8 GiB of space, not 12.

Now let us dissect the 9.8 GiB still further. What do you get on Windows RT that you don't get on iOS?

- Office RT. My x86 Office 2013 is 2 GiB, but Office RT includes fewer applications. Assume Office RT takes up 1.0 GiB.
- Drivers. My x64 Windows 8 install has 0.8 MiB of drivers, but Windows RT has a reduced driver set. Call it 0.5 GiB.
- Fonts, many of them bundled with Office. My install has 0.3 MiB of fonts. Fonts don't shrink when ported to ARM.

If you accept that these are worth the 1.8 GiB they take up, then we're now down to 8 GiB that can really be attributed to Windows RT and "a bunch of apps."

That includes the pagefile (about 1 GiB on a system with 2 GiB RAM), IMEs for a whole boatload of languages (the dictionaries for simplified Chinese alone are about 60 MB), etc.

Edited 2012-10-20 01:25 UTC

Reply Parent Score: 7

RE[2]: Not quite true
by Laurence on Sat 20th Oct 2012 01:37 in reply to "RE: Not quite true"
Laurence Member since:
2007-03-26

And it's not even 12 GB. It's actually 9.8 GiB.

I can't believe nobody has pointed this out yet.

What Microsoft actually said on that Reddit thread was that "After the OS, OfficeRT and a bunch of apps, you will still have more that 20GB." Thus, they did not say that disk usage was 12 GB. They said that free space was 20 GB.

Ah, but how did he get that free space figure? Probably in Windows Explorer -- which reports free disk space in binary gibibytes, even though it uses the "GB" abbreviation. Yet flash memory is sold using decimal gigabytes. My "128 GB" SSD is reported as "119 GB [= GiB]" in Windows Explorer.

A 32 GB flash drive = 29.8 GiB. If you have "more than 20 [GiB]" of free space remaining, then that means the entire running system takes up 9.8 GiB of space, not 12.


AFAIK SSDs do actually report the space correctly. What actually happens is not the entire SSD volume is available to fill; some is always reserved for load wearing (thus extending the lifetime of the unit).

The reason being that SSDs use a CoW method (copy-on-write) and if you had a full SSD, then there's less free block to write each fs update too. Thus you're forced to recycle the same blocks (which is very bad for the lifetime of solid state drives). However as modern SSDs keep a little bit of space back, it means there's a greater pool of free blocks to balance the writing across.

So a 120GB SSD does actually have 120GB of storage but you're only allowed to fill ~120GB as the remainer is there purely for load wearing.

I hope that makes sense, i should have been in bed 2 hours ago so it's probably not the clearest post I've made lol

Reply Parent Score: 2

RE[3]: Not quite true
by tanzam75 on Sat 20th Oct 2012 02:02 in reply to "RE[2]: Not quite true"
tanzam75 Member since:
2011-05-19


So a 120GB SSD does actually have 120GB of storage but you're only allowed to fill ~120GB as the remainer is there purely for load wearing.



That the 7% overprovisioning factor happens to be the same as the difference between GiB and GB is a nice coincidence. But it's just that -- a coincidence.

The coincidence disappears when you look at drives that have RAISE. See, e.g., the 960 GB OWC Mercury Electra MAX 3G SSD: http://www.anandtech.com/show/6038/owc-releases-960gb-mercury-elect...

It has 1024 GiB of raw capacity, and 894 GiB of formatted capacity. The difference is not 7% but 14% -- and it's because some of the raw capacity is reserved for RAISE as well as overprovisioning.

They're advertising this as a 960 GB drive (= 894 GiB), not as a 1024 GB or a 1 TB drive. In other words, they're not advertising the raw capacity in binary prefixes, but the formatted capacity in decimal SI prefixes.

Magnetic hard drives also had a higher raw capacity than formatted, as did floppy disks. Because the difference wasn't anywhere close to the 5% difference between MiB/MB or the 2.4% difference between KiB/KB, the urban legend did not have a chance to spawn as it did with SSDs.

(Trick question: Why are 1.44 MB floppies called that? They're neither 1.44 decimal MB, nor 1.44 binary MiB, nor 1440 decimal KB, nor 1440 binary KiB.)

Edited 2012-10-20 02:15 UTC

Reply Parent Score: 3

RE[2]: Not quite true
by HappyGod on Mon 22nd Oct 2012 03:10 in reply to "RE: Not quite true"
HappyGod Member since:
2005-10-19

The whole "ibibyte" nomenclature should be dropped as far as I'm concerned.

It may be syntactically correct in terms of the metric prefixes v binary etc. But all their introduction has done is cause massive confusion as different storage units utilise the term in different ways (i.e. HDD use metric GB, while RAM uses binary).

The "ibibyte" usage was just a result of HDD manufacturers adopting it to enable them to sell a 1TB drive, that was "technically" 1TB, but was actually about 92GB less than that, according to Windows, and pretty much everyone else that studied Computer Science up until that point!

When I studied, a gigabyte was 1024-cubed bytes. Metric system be damned.

Just ask Google:

http://tinyurl.com/93y3m4b

Edited 2012-10-22 03:17 UTC

Reply Parent Score: 2