15' rMBP + SDXC card?

Petulka

macrumors regular
Original poster
Jan 22, 2010
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Would it be possible to use the (most likely) 64GB SDXC card as "second HDD"?
 

B...

macrumors 68000
Mar 7, 2013
1,949
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Yes, just the concerns are: no deep sleep, and it sticks out.
 

ColdCase

macrumors 68030
Feb 10, 2008
2,962
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I've had a micro 64GB in a minidrive installed all the time for over two months now. The access to the SD card is slow, something like a USB stick. Works fine for downloads and temporary storage. Wouldn't suggest trying to boot from it.

If you use something like Jetison to unmount drives on sleep, it won't remount the SD card.

Most SD card are formatted fat32, I'd advise reformating to macOS extended for fewer quirks.

A mounted SD card will prevent deep sleep (hibernate) if thats important to you.

Using the SD slot to augment storage is routine for many MacBookAir users where they have tiny hard drives.
 

dtziheucdavis

macrumors newbie
Jan 26, 2013
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I wish I had known about the minidrive earlier. When I got my macbook air 128gb in 2011, I quickly ran out of memory space and purchased a very expensive 128gb SD card to stick in it and use for storing files. It worked well but one day I used another bag to carry my laptop and sure enough, the card snapped. Do keep in mind the card access speed is quite slow though.
 

NewishMacGuy

macrumors 6502a
Aug 2, 2007
636
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The access to the SD card is slow, something like a USB stick.
Do keep in mind the card access speed is quite slow though.
The micro cards are still pretty slow, but the fastest regular cards are almost as fast as an HDD these days (though that will seem slow compared to the stock SSD). Give it a couple more years and you'll probably be able to get a 128GB micro that's HDD fast.


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dastinger

macrumors 6502a
Mar 18, 2012
818
3
The micro cards are still pretty slow, but the fastest regular cards are almost as fast as an HDD these days (though that will seem slow compared to the stock SSD). Give it a couple more years and you'll probably be able to get a 128GB micro that's HDD fast.


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If I was interested in something like this, what would be the best option regarding speed? Let's say 64GB.
 

duervo

macrumors 68020
Feb 5, 2011
2,309
1,032
Nope, writes are horribly slow to SDHC cards, unless you start looking at UHS Class cards, and that's just talking about theoretical spec-type numbers, not real-world. Speaking theoretical only, and if you want decent write speeds, don't even bother with Class 10 or below. With Class 10, we're talking a maximum of 30MB/sec (albeit with a minimum rating of 10MB/sec). Also, some manufacturers are selling SDHC cards that they classify as UHS Class 1, but are merely Class 10 cards from a performance perspective, so buyer beware where those are concerned.

Still speaking theoretical performance here, and not feasibility of using in a MBP, if you want anything like a HDD with flash-based storage, without jumping to SSD, you probably need to look at Compact Flash or UHS Class 1 SDHC for now, which can get comparable performance to HDD's, but even then, it's only theoretical speeds. Speeds on paper. Real-world results will most definitely be slower. Cost per GB is still more expensive than a traditional HDD, too.

Don't get me wrong, I was all for the whole SDHC as additional storage idea when I tried it. I loved the idea of stuffing all my TV shows and movies onto a couple dozen SDHC cards and storing them like poker chips ... sounded great, but UHS cards were much too expensive at the time I checked into it, and Class 10 took much too long for my taste to fill up a 64GB card. They just aren't where they need to be in order to be used to replace HDDs. Real-world performance results were very unimpressive. Realistically, IMHO, they are only useful for storing media ... music, photos, and videos, but be prepared for a long haul when doing the initial copy of media onto them. Start the job, then go browse the net, go for lunch, or have a coffee or something.

I should probably add that I haven't bothered looking into SDXC yet, aside from looking at the specs. Specs for them, like the SDHC, are unimpressive. Don't expect to be coming close to the max transfer rate with those on writes. Just not comparable at all to modern HDD's. Maybe to HDD's 6 or 8 years ago, but not now. Compact Flash are still the king of them all on theoretical performance and capacity for now. They just fail on physical footprint compared to everything else out there.
 
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Petulka

macrumors regular
Original poster
Jan 22, 2010
104
0
I was planning to use it for movies, music etc. with low expectations. I might get 500GB external HDD or double the price for 1TB but I don't really want to carry it around.
 

NewishMacGuy

macrumors 6502a
Aug 2, 2007
636
0
If I was interested in something like this, what would be the best option regarding speed? Let's say 64GB.
Probably the SanDisk Extreme Pro SDXC cards. They claim 90MB/s as max speed for writes. In the real world you'll probably get something less than that, but that will be pretty close to your HDD speed. My 7200rpm HDD does slightly less than 95MB/s on BlackMagic.

They're not cheap, but they are small and fairly tough!

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ColdCase

macrumors 68030
Feb 10, 2008
2,962
142
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I use a SanDisk Ultra 64 GB MicroSDXC Class 10 UHS-1 Memory Card in a 2013 rMBP. The BlackMagic benchmarking tool measures 10MBps writes and 44.5 MBps reads. A typical inexpensive rotational drive in a USB 2.0 enclosure measures 22MBps writes and 33MBps reads. I hear the full sized SDXC cards are a bit faster but as of a month ago the extreme pros were not available in the microSDXC form factor.