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Fusion drive with micro SD(niftydrive) and rMBP

JSENNY25

JSENNY25

macrumors regular
Original poster
Sep 12, 2008
205
64
Ohio
I was hoping that someone either has tried to create a fusion drive with their rMBP and a microSD or if someone knew if it was possible.

I think that this would be interesting to expand storage that is semi permanent and an enticing option instead of buying the 480 GB SSD from OWC, but, I am not sure if it would work.

I realize with the niftydrive you can store entire folders (iTunes) on the SD, but as technology increases, the price of the microSD may go down and the size may go up.

Are there any people out there who know if this is a possibility?
 
Last edited:
RE: about that Fusion Drive...

Hi JSENNY25,

Great idea! But I think there are some issues to consider.

Apple does not officially support Fusion Drives with external drives, although they can be manually setup. The question is "Why?", and the answer is "I don't know", but I can speculate. External drives are more prone to being accidentally disconnected before being properly unmounted. What happens when one physical disk of the logical CoreStorage Fusion Drive (FUD) partition suddenly goes "off-line"? I suspect this make the FUD inaccessible, at least for a short time. How does one recover from such an event? There also must be ways to recover from having one drive of a FUD fail, but I haven't yet seen much discussion on this. I would certainly make sure that I had an external bootable drive before attempting to make a FUD with the SSD in my rMBP and a microSD in the SDXC port.

Lastly, I've also read about connection issues for SDXC/microSD drives. Sometimes they seem to disconnect unexpectantly and repeatedly. I think this would also reek havoc with a FUD. Once again, there are probably routines that handle such connection issues for FUDs, but I haven't seen much discussion nor any experiments testing these issues yet.

Good luck, and if you try this, please let us know how it works,
Switon
 
All good points

MCAsan said:
where would the second drive be installed inside an rMBP?
Click to expand...

switon said:
Hi JSENNY25,

Great idea! But I think there are some issues to consider.

Apple does not officially support Fusion Drives with external drives, although they can be manually setup. The question is "Why?", and the answer is "I don't know", but I can speculate. External drives are more prone to being accidentally disconnected before being properly unmounted. What happens when one physical disk of the logical CoreStorage Fusion Drive (FUD) partition suddenly goes "off-line"? I suspect this make the FUD inaccessible, at least for a short time. How does one recover from such an event? There also must be ways to recover from having one drive of a FUD fail, but I haven't yet seen much discussion on this. I would certainly make sure that I had an external bootable drive before attempting to make a FUD with the SSD in my rMBP and a microSD in the SDXC port.

Lastly, I've also read about connection issues for SDXC/microSD drives. Sometimes they seem to disconnect unexpectantly and repeatedly. I think this would also reek havoc with a FUD. Once again, there are probably routines that handle such connection issues for FUDs, but I haven't seen much discussion nor any experiments testing these issues yet.

Good luck, and if you try this, please let us know how it works,
Switon
Click to expand...

I may give this a try...but I the more I think about it, having the NiftyDrive and must managing what I may have in there is pretty much the same thing. It just won't be as "cool" as saying it is a fusion drive.

If I placed my iTunes and my stored photos (large folders/apps that are not used as often as others) on the SD card it would essentially be pretty similar.
 
I never thought about using a MicroSD as a second storage unit. I was doing reading in which they can achieve 2TB of space on them. If that becomes mainstream and at the right price that would be really cool. I hardly use my SD slot (I have CF cards for my camera).

I would assume that they would cost a lot though for that much memory.
 
For some of the reasons stated above I would not try to do fusion drive in this way. It seems like Fusion is doing block level management, meaning that part of a file could exist on one drive and another part on the other drive.

That could cause pretty bad issues if the SD card were to ever have connection problems. It isn't like Time Machine which is made to handle the external drive being connected and disconnected.
 
RE: FUDs...

JSENNY25 said:
I may give this a try...but I the more I think about it, having the NiftyDrive and must managing what I may have in there is pretty much the same thing. It just won't be as "cool" as saying it is a fusion drive.

If I placed my iTunes and my stored photos (large folders/apps that are not used as often as others) on the SD card it would essentially be pretty similar.
Click to expand...

The way a FUD works is to promote 128kB blocks that are read often to the faster SSD disk and demote 128kB blocks that are the least used from the SSD to the slower disk. This is a good thing in terms of performance, as it does not have to promote the entire file (which could be many GB in size). But it also means that if the slow drive (say the microSD) goes off-line then the SSD may only contain portions of the files that you are currently reading, with the remaining portions still on the microSD that is now off-line. We would hope that the Mac OS and CoreStorage handles this situation with aplomb and does not force a kernel panic or anything, but who knows? Perhaps someone has tested this already, but I haven't seen it. Again, with the connection issues that the microSD cards appear to have in the SDXC port, I'd worry about building a FUD with a rMBP's SSD and a SDXC microSD card for fear of potentially corrupting the kernel. Make sure you have a bootable external drive before attempting this.

And get back to us with the results after you do so, please.

Switon
 
RE microSD...

theuserjohnny said:
I never thought about using a MicroSD as a second storage unit. I was doing reading in which they can achieve 2TB of space on them. If that becomes mainstream and at the right price that would be really cool. I hardly use my SD slot (I have CF cards for my camera).

I would assume that they would cost a lot though for that much memory.
Click to expand...

Hi,

Correct me if I'm wrong, but while SDXC cards can theoretically have 2TB, today most commercially available cards are much smaller. In fact, it is somewhat difficult to find SDXC cards above 256GB. CF cards come bigger, though. And most microSD cards available today max out at 64GB. Last month a UHS-1 microSD card was announced, but I haven't seen it yet. If you don't mind spending big bucks, and don't mind a small protrusion out the side of your laptop, then a 128GB SDXC 600x card is available and the 256GB 600x card has been announced. These are at least fairly fast cards. CF cards are even faster, with 800x and 1000x available.

Switon
 
The largest micro sd card at the moment is 64GB. However it would be awfully slow! 60Mb read/write. certainly no SSD drive. Or a regular hard-drive for that matter
 
what the OP is talking about is a tool that uses a Micro SD card which to the best of my knowledge tops at 64gb for about $40 depending on what you get I would recommend a class 10 (higher read/write speeds) micro sd if you're planning on using it for this purpose. Nifty drive actually takes the micro SD and makes it flush with the side of your MBP so essentially just looking at your laptop you'd never suspect there was even and SD card slot.

MiniDrive_Pro_Mkr2_F_B_Silver_v1_1024x1024.png


I actually thought about this a couple of days ago because I watched a video on how to create your own fusion drive in a cMBP but since I have retina obviously I won't be just installing a secondary hard drive. If anyone tries this please post back with details and performance.
 
tmanto02 said:
The largest micro sd card at the moment is 64GB. However it would be awfully slow! 60Mb read/write. certainly no SSD drive. Or a regular hard-drive for that matter
Click to expand...

Yes, that's what I thought ... the largest microSD cards available today are 64GB. I did see an UHS-1 64GB microSD card announced last month, but I don't know if you can purchase these yet.

Thanks,
Switon
 
switon said:
Yes, that's what I thought ... the largest microSD cards available today are 64GB. I did see an UHS-1 64GB microSD card announced last month, but I don't know if you can purchase these yet.

Thanks,
Switon
Click to expand...

Of course if you had an "array" like this, and a few Class 10 microSDHC cards.:
http://www.photofast.tw/products.asp?pid=65 ~$50 USD

1,500.00 TWD = $51.57 USD
Taiwan New Dollar ↔ US Dollar

If only it worked with the 32GB cards:
http://www.staples.com/Polaroid-32G...Flash-Memory-Card/product_730752#revs_content
128GB, $100, 80MBytes per second = 640Megabits per second (limit of USB 2.0 is 480Mbps or 60MBps)

May get some of these to enable Readyboost in Windows 8 (even if it only gets up to 64GB of cache).
http://www.bleepingcomputer.com/tutorials/using-windows-readyboost-to-increase-performance/
 
Last edited:
RE: speeds of SDXC...

Hi,

I see that you can buy a SanDisk Extreme Pro SDXC card that has read speeds of 95MB/s (633x) and write speeds of 90MB/s (600x). These speeds aren't quite there yet, but they are getting closer to what you find in practice for USB3 external HDDs for sequential read/writes. Of course, the 95MB/s and 90MB/s are SanDisk's "max" specifications, and thus the "in practice" speeds will more than likely be slower too. I'm a little intrigued by the Lexar 1000x CF cards ("150MB/s or faster" "minimum sustained read" spec). What sequential speeds, in practice, do these cards achieve? Can one of these 1000x CF cards effectively replace an external USB3 HDD, speed-wise? Of course, for the price of one of these 128GB CF cards you could buy a Pegasus J2 512GB Thunderbolt with roughly 770MB/s read and 680MB/s write speeds and still have several hundred dollars left over to spend.

Switon
 
I was stupid enough to do this

Got the rMBP 15" back in November and put in a 128 Gig SD card. The box has 256 Gig SSD and 16 Gig Ram, 2.3 CPU. So I get 375.48 Gig of Fusion disk. Currently it is eating into the SD card space a bit. I have 93.15 Gig free and you do notice the speed hit but I figure that I will be forced to keep the box clean and as close to 256 gig as possible. The real goal is to be able to do this when SDCX cards are smoking fast, big and cheap. So now this is just a test. The down side could be when someone pulls the SD card for some lame reason. That would not be good. The setup is as easy as you would expect. I also use ZFS on external HD's which is problematic as when you either plug in the thunderbolt or un mount the disks, it tends to kernel panic. So fingers crossed and I will report back if this proves to be a bad idea. I do like the idea that $125 on a 50 MB/sec 128 Gig SD card can give me some breathing room on top of the SSD's. The SSD's I will upgrade down the road a few years or just get the bigger SD card once they get bigger size, and better performance.
 
The Read/Write speed to the fastest micro SD card on the market right now are more that half as slow as a 5400rpm HDD. to do this right now would be pointless because if it worked it would be painfully slow.
 
I really don't see the point. As far as I can see, even full size SSDs don't really get much faster than around 50MB/s, which is a tenth of the speed of a proper SATA 3 SSD. And they aren't much cheaper either.

The whole point of the Fusion drive is to combine a slow, large storage medium with a fast, small storage medium. Therefore combining a large, fast SSD with a small, slow SD card would defeat the purpose.

I can see the appeal in quickly and easily adding 128-256GB of storage to your computer, but it would be far better to just leave it as a secondary drive on your desktop, rather than trying to do any fancy drive combining or RAID.

EDIT: Still, larsgm, kudos for doing it, pointless as it may be :p
 
larsgm said:
Got the rMBP 15" back in November and put in a 128 Gig SD card. The box has 256 Gig SSD and 16 Gig Ram, 2.3 CPU. So I get 375.48 Gig of Fusion disk.
Click to expand...

I just cannot understand why anyone would try this. The point of a fusion drive is to get the capacity of a big slow spinning disk, at the speed of an SSD. Making a fusion drive with a slow SD card has no advantages at all.
You'd even be better off with a USB 3.0 external disk.

Further, the risk of data loss by accidentally removing the SD card is far too high.
 
Well, there are some situations where you might think about this. And I've got one at hand right now.

I'm using my 13" MBA for deejaying and that is pretty much the only purpose of the laptop. It has a 128gb SSD which is quite soon running out of space.

Now, I have purchased a nifty mini drive and a 64gb micro sd card inside it. Why I'm seriously thinking about trying how Fusion Drive would work with this setup is that if I have two disks, I will also need to have two different Serato libraries. And as my library is already quite huge and built in a certain way (label/cat#/songs) and Serato Scratch won't look for my files if they are moved to a different folder, I would have to rebuild my whole library if I were to have two disks.

So in this type of a case FD really makes a lot of sense.
 
I know that Dell servers will let you order two 2GD SD cards in RAID so that you can book VMware server off of them instead of using a SSD, and then you can use the full storage to be your storage RAID.
 
I tired it - Fusion 256GSSD + 64GmicroSD

I tired it last night 256G SSD + 64G microSD. TOO SLOW when memory swap happens.... Going back tonight.
 
mwkchan said:
I tired it last night 256G SSD + 64G microSD. TOO SLOW when memory swap happens.... Going back tonight.
Click to expand...

Why on earth would you do that? The purpose of a fusion is to marry a high-speed drive (typically smaller), with a slower speed drive (typically larger), to achieve a useful balance of size, speed and cost.

The SD slot is mounted on the internal USB hub AFAIK, so is slow, much much slower than the SSD you have. The SSD is also much larger so most of your data will already be on the faster drive.

:confused:
 
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