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Old 05-01-2012, 03:49 AM   #1
Steelbom
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Default What's the difference between an SD card and the internal storage say in an iPhone?

Hey,

I'm wondering what the difference is between even the best SD card (class 10) and the internal storage used in devices such as the iPhone or Android based smartphones? Is it slower? Less reliable? More expensive?

Would appreciate any info, thanks
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Old 05-01-2012, 04:02 AM   #2
dma0991
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It could be slower. Reliability probably not much as you could easily replace a dead SD card but a dead memory on the logic board is difficult to replace and in some cases the whole unit is replaced. Considering SD cards can be bought for very little money, it isn't that expensive.

In terms of ease of use, I'd like a SD card to go with internal memory. It is one of my gripes about Apple products as I own an iPod myself. Getting data in and out is difficult compared to an Android that does support SD cards. In the end, these constraints give opportunities to Kingston, Seagate and Transcend to create drives that connects wirelessly to the device which seemed kinda redundant as price/GB is way more expensive than having a SD slot or more internal memory.
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Old 05-01-2012, 04:07 AM   #3
Steelbom
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Quote:
Originally Posted by dma0991 View Post
It could be slower. Reliability probably not much as you could easily replace a dead SD card but a dead memory on the logic board is difficult to replace and in some cases the whole unit is replaced. Considering SD cards can be bought for very little money, it isn't that expensive.

In terms of ease of use, I'd like a SD card to go with internal memory. It is one of my gripes about Apple products as I own an iPod myself. Getting data in and out is difficult compared to an Android that does support SD cards. In the end, these constraints give opportunities to Kingston, Seagate and Transcend to create drives that connects wirelessly to the device which seemed kinda redundant as price/GB is way more expensive than having a SD slot or more internal memory.
I see, thanks. You could replace a dead SD card but you'd lose your data if it wasn't backed up. Are SD cards less reliable than the internal storage these devices use?

I'm curious why they just wouldn't stick an SD card inside rather than use any kind of internal storage, it's much smaller and pretty cheap.
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Old 05-01-2012, 04:14 AM   #4
dma0991
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Quote:
Originally Posted by Steelbom View Post
I see, thanks. You could replace a dead SD card but you'd lose your data if it wasn't backed up. Are SD cards less reliable than the internal storage these devices use?

I'm curious why they just wouldn't stick an SD card inside rather than use any kind of internal storage, it's much smaller and pretty cheap.
A dead internal memory that is not backed up would meet the same fate of losing data as well. I would usually reserve the SD storage for data that I want it to be there temporarily like picture, videos, etc where I am quite sure it is just a copy from my PC.

I don't have any data to back up the claim that SD cards are less reliable but having an internal storage would be faster than a SD. I believe SD cards are best left as a form of secondary storage.
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Old 05-01-2012, 04:22 AM   #5
Steelbom
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Quote:
Originally Posted by dma0991 View Post
A dead internal memory that is not backed up would meet the same fate of losing data as well. I would usually reserve the SD storage for data that I want it to be there temporarily like picture, videos, etc where I am quite sure it is just a copy from my PC.
That's true, I was just thinking of it in terms of being replaced with SD cards. If the reliability is the same, and the latter is much smaller and maybe even cheaper as well, why wouldn't it be used?
Quote:
I don't have any data to back up the claim that SD cards are less reliable but having an internal storage would be faster than a SD. I believe SD cards are best left as a form of secondary storage.
Mmm, I see. Thanks for the info.
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Old 05-01-2012, 09:45 AM   #6
exdeath
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SD card is a serial SPI interface limited to 25-50 MHz and bottlenecked by a SD-NAND controller chip in the SD card.

Internal memory is native NAND in parallel running at the maximum speed of the NAND. Also, internal memory may use multiple NAND chips in parallel for higher speeds, while and SD card is limited to 2 chips at most.

In other words SD cards are well known to be very slow.
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Old 05-01-2012, 10:08 AM   #7
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SD card is a serial SPI interface limited to 25-50 MHz and bottlenecked by a SD-NAND controller chip in the SD card.
I see. Err, what would the speed of the interface be for internal memory. And what's wrong with the controller chip in the SD card? (If you don't mind explaining more, thanks.)
Quote:
Internal memory is native NAND in parallel running at the maximum speed of the NAND. Also, internal memory may use multiple NAND chips in parallel for higher speeds, while and SD card is limited to 2 chips at most.

In other words SD cards are well known to be very slow.
Ah I see, thanks for the info. So... what kind of speeds would you be looking at for internal memory vs class 10 SD cards? Is it 20MB/s vs 10MB/s respectively?
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Old 05-01-2012, 11:29 AM   #8
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on-board NAND also has better random read/write specs in general and most certainly compared to class 10. Class 10 devices are optimized for contiguous read and write. There are class 4 and 6 cards that beat the pants off class 10 as a random access device.
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Old 05-01-2012, 09:23 PM   #9
Steelbom
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on-board NAND also has better random read/write specs in general and most certainly compared to class 10. Class 10 devices are optimized for contiguous read and write. There are class 4 and 6 cards that beat the pants off class 10 as a random access device.
Ah, I see. Thanks, that's good to know.
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