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[2]: Not quite true
by Laurence on Sat 20th Oct 2012 01:37 UTC in reply to "RE: Not quite true"
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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

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