If I were to purchase a new MacBook Air, the 11", 64 GB model, I turned it on and did a “Get Info” on the disk (yes, I know, more technically “flash storage”), how much free space would there be? In other words, how much space do the OS and built-in applications take up?
I can understand why Apple wouldn’t freely state that information, but it’s kind of important in a buying decision to know how much of the 64 GB I can actually expect to use for the applications and data I might want to have on it, especially when 64 GB is a bit small by today’s standards. (And before anyone points it out, I know that an Air is not meant to be a primary computer, I don’t intend to use it as such, but it would still be nice to know if the stuff I’d like to have on it will reasonably fit, or if I’d pretty much need to spring for the 128 GB model in order for it to be usable).
As it happens, I have one of these sitting on my desk right now (the 128 GB model). It has all the latest software updates but nothing else installed - 11.8 GB used. Interestingly, the drive reports a total size of 121.3 GB, which I assume is due to formatting overhead.
All in all, I would expect the 64 GB model to have approximately 48 GB free.
Note that various companies will be selling replacement SSD boards with higher capacity (e.g. 256 GB) that you can always upgrade to later.
I think that the descrepency between the advertised drive space of 128 GB and reported drive space of 121.3 has something to do with the units used to advertise computers compared to units the drive measured. I thought we had a pretty lengthy discussion on this one time. Wikipedia explains it here.
Actually not. In Mac OS X 10.6, Apple switched to using SI prefixes (i.e. decimal units) to display file sizes and drive capacities. This is the same unit system that hard drive manufacturers use, and so in 10.6 there is no longer a discrepancy due to unit choice.
Windows, and previous versions of Mac OS X, use binary units, which did cause a discrepancy as you described. The correct notation for this unit is GiB, or the abysmally-named gibibyte.
However, there is something else going on here, because OS X is reporting the 128 GB SSD as a total capacity of 121.3 GB, while it reports my 250 GB conventional hard drive as a total capacity of … 250 GB! Maybe the SSD is slightly smaller than advertised.
Okay, apparently the discrepancy between the 128 GB advertised capacity and the 121.3 GB reported capacity is that the drive controller sets aside some “working space”.
Yeah, an ssd needs a bit of shuffle-shit-around space to operate. If you’re interested in the technical reasons for this, head over to anandtech and read a series of articles and reviews of ssd’s dating back a couple years. I don’t actually recommend this, as the articles are quite a slog, but it explains a lot of stuff about why ssd’s behave the way they do.