SDHC iso SDD

iGrf

macrumors newbie
Original poster
Nov 12, 2007
24
0
I've read through most of the SDD buying guide and saw somewhere that even booting OSX from and external USB drive give a significant speed advantage.

Does this mean that you could use an SDHC card (available in 64 or 128 Gb) as a boot/system disk and enjoy the same speediness ?

That way you can keep the internal harddisk for data and move the system to a flash based storage that easy to install etc.

Off course you lose the SD slot in the process but you can keep the optical drive.

Has anybody tried this ?

Or is it a stupid idea ?

PS : I'm looking at replacing my 2007 iMac with a MBP and would like to have both SDD speed and HDD diskspace :rolleyes:
 

MarkMS

macrumors 6502a
Aug 30, 2006
992
0
Macs utilize the USB bus to communicate with the SD card, so essentially using an SDHC card is like using a USB flash drive. Macs use USB 2.0, which tops out at around ~40 MB/s. Pretty slow compared to a SSD/SATA II or SATA III combo that can start at around 250MB/s on SATA II and now up to 500MB/s read speed with SATA III. If we were talking USB3, then it might be worth it. But for now, it's not worth it unless you wanted to make an emergency bootable OS X drive to save important files if something happened to the drive or original OS X installation.

Do yourself a favor and get a SSD, preferably Intel or Crucial M4, since those have been the most reliable. OWC is also good, but not as reliable as an Intel/Crucial in my opinion. Also get a data doubler (aka hard drive caddy) from Amazon that replaces the optical drive and a cheap optical enclosure from there too. Best $400 I've ever spent. $350 for the Intel SSD and $50 for the caddy and optical enclosure. Used my stock 320GB for media and bootcamp. My 2009 MBP has been reborn and I feel like it will last me another 4-5 years easily.

Hope this helps.
 

mulo

macrumors 68020
Aug 22, 2010
2,267
5
Behind you
I think even the fastest SDHC cards currently are slower than USB 2.0.
this is true to some extent...

the thing is that hosting an operating system requires very low random access read times, which is what flash storage is great at, so in short transfer speeds will be slower to and from the SD card, (buy a SanDisk Extreme Pro and it won't!) but random access will be much faster, thus making the operating system run smoother.

its the same deal as with processors, people are blinded by their frequency (Ghz) when, this really isn't what matters much at all.
Anyway in this case, what you want is fast random read and write access, not sustained transfer speeds.
 
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thundersteele

macrumors 68030
Oct 19, 2011
2,984
7
Switzerland
Macs utilize the USB bus to communicate with the SD card, so essentially using an SDHC card is like using a USB flash drive. Macs use USB 2.0, which tops out at around ~40 MB/s.
This is not true. The SD card reader is not connected to the USB bus on my MBP.

this is true to some extent...

the thing is that hosting an operating system requires very low random access read times, which is what flash storage is great at, so in short transfer speeds will be slower to and from the SD card, (buy a SanDisk Extreme Pro and it won't!) but random access will be much faster, thus making the operating system run smoother.
Ok, it is true that pure transfer rates are not everything. But SD cards are optimized for large sequential read/writes, since they are mostly used in cameras and to transfer photos to another HD. The access times might be good, but the random read/write is still very slow, which is probably not good for a system disc. Don't forget that a SSD is not just a bunch of flash chips, a very important part is the controller.
 

MarkMS

macrumors 6502a
Aug 30, 2006
992
0
This is not true. The SD card reader is not connected to the USB bus on my MBP.
My bad, I'm still rocking an 09 MBP. I had no idea the 2011 models have their SD slot connected via PCIe. Thanks for pointing my error out! :D
 

mulo

macrumors 68020
Aug 22, 2010
2,267
5
Behind you
Ok, it is true that pure transfer rates are not everything. But SD cards are optimized for large sequential read/writes, since they are mostly used in cameras and to transfer photos to another HD. The access times might be good, but the random read/write is still very slow, which is probably not good for a system disc. Don't forget that a SSD is not just a bunch of flash chips, a very important part is the controller.
this doesn't matter much
Operating systems are shattered into an oblivion of tiny files, any semi-decent SD card will outpace almost any HDD reading all these files, despite crappy throughput. thus making both booting and running the OS faster.
apps like Adobe Photoshop which are also obliviated into a gazillion files will also launch and run faster from a SD card.

in any case, all the OP has to do is insert a SD card, install OS X onto it, and see if it works for him, if not format the card and he'll return to the OS on his hdd? (might need to select startup disk, hold option during boot to select OS to boot)
 

squeakr

macrumors 68000
Apr 22, 2010
1,603
1
Is the Sd slot even available as a bootable device?? I didn't think it was available to boot from in newer MBPs. Can someone who knows for sure (as in has actually done it and gotten it to work as a bootable device) chime in here?
 

iThinkergoiMac

macrumors 68030
Jan 20, 2010
2,666
4
Terra
Is the Sd slot even available as a bootable device?? I didn't think it was available to boot from in newer MBPs. Can someone who knows for sure (as in has actually done it and gotten it to work as a bootable device) chime in here?
I've read enough to know it is. Not done it myself, but it's a well-documented fact.
 

DWBurke811

macrumors 6502a
Jun 10, 2011
820
1
Boca Raton, FL
this seems like you're "fixing" a problem that doesn't exist, by causing more problems...

not only are you stuck with a card hanging out of your laptop, and much slower speeds than a real ssd, but a 128GB sdxc is the same price(or more?) than a 120/128gb sata3 ssd.