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retailacc

macrumors member
Original poster
Jun 19, 2017
41
23
Boston, MA
Hello guys,

So everything I read that contains the words 2018 MacBooks Pro SSDs says that they're the fastest ever, and quoting 2.5K read/write speeds.

This is obviously great news, but I am wondering if this is specific to the more expensive higher capacity configurations. It is not uncommon for manufacturers to limit performance on smaller drives.

Does anyone know if the entry level 13" / 15" 256GB SSD is also able to do 2.5K read/write?
I really don't need more than 256GB as I only work on a single project at a time before archiving into a storage HDD, but I will appreciate the SSDs speeds.

Thank you in advance!
 
It is not uncommon for manufacturers to limit performance on smaller drives.
It's not that they limit anything as such, typically. It's because flash memory really isn't all that fast in of itself (goes doubly for MLC or especially TLC flash which is only a small fraction of SLC flash speed.) To make a really fast flash SSD, many flash memory dies are accessed in parallel, but in smaller drives you have fewer dies, so less parallelism, and thus a slower drive.

You could retain speed by using more lower-capacity dies rather than a few high capacity dies, but that is typically more costly. So it depends on what Apple is doing, and from what I've seen nobody has tested different capacity drives yet - probably because it requires multiple laptops, and the large capacity drive versions are super expensive.

Anyway, Apple's specs are typically not attainable in most real-world usage scenarios; flash drives only hit max read or write speed with large block size linear reads or writes, which basically only happens during large file writes/copies. So unless your work exclusively involves copying very large files again and again, you won't hit stated performance figures anyway. :p
 
For perspective on real world experience, it's almost exactly 2x faster at decompressing large files than the 2014 15" MacBook Pro.
 
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