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Does the iPad use any type of controller for drive wear leveling? It seems like Sandforce is the only player in the field.

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migrated from superuser.com Feb 20 '11 at 17:10

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3 Answers 3

Whether Flash is used in an SSD (SATA interface) or just as a Flash memory hanging off any other internal bus, the Flash wearing out issues are the same. Unless Apple has done something in system software to minimize write cycles (caching schemes?) the wearing out risks are real and only Apple can explain how it is mitigating it. Yes, SandForce controller is the only one that claims Write cycle reduction and thus extend the Flash endurance by minimizing the write cycles.

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This isn't a big concern since you will likely be writing to flash less than you would on a desktop. Streaming video will go to DRAM. I'm an electrical engineer who uses flash and I would be ok buying an iPad; I expect the battery will fail long before the flash. Additionally when a sector goes bad, it will be skipped on future writes.

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Apple iPad does not use an SSD. It uses a flash based drive.

UPDATE: In response to the differences between SSD's and Flash Drives, here is the following excerpt explaining the difference.


‘Flash Drives’ are a generic term which used for anything from USB memory sticks to SSDs. An USB flash drive uses lower quality low performance NAND flash with just 1 or 2 channels. Its durable, cheap but slow. An SSD on the other hand uses high performance NAND with mutliple channels. ( 12 or 8 is not uncommon), and there is a memory controller on a SSD which is much better and both can store data even if its not powered. Flash drives (USB) are slow storage devices where as SSDs are high performance drives. They’re much faster than normal HDDs.

A USB flash drive uses USB, which is generally a slower interface than the Serial ATA interface. A USB flash drive is generally thought of as a removable device by the OS and is managed as such. A SSD is treated similarly to a hard drive, and is often recognized by your OS as a type of fixed disk.

USB flash drives and solid-state drives are both based on flash memory. Most of the flash memory use NAND memory, which are available as single-level cells (SLC) and multi-level cells (MLC). Single-level cells store a single bit in a single memory cell, whereas multi-level cells store more than a single bit in a single memory cell. The MLC accomplishes this by allowing each memory cell to store multiple electrical states, therefore, allow one MLC cell to store more information than one SLC cell. For example, a MLC that uses 4-levels can store 2 bits of information. MLC are cheaper, as they can store more information per memory cell than SLC. Cheap, large SSDs and USB flash memory use MLC disks, although not necessarily. MLCs sounds great in terms of storage density, but it does have a catch. MLCs are slower than SLC. Therefore, the large capacity USB flash drives and SSDs tend to be slower. Solid-State Drives (SSDs) have no moving parts, high reliability and longer life-span than traditional hard drives

Taken from here

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-1 DUH same thing –  Hello71 Feb 19 '11 at 23:42
    
Solid State Drive is very different from a flash based drive. Learn to do your research before voting down. SSD uses more NAND than a normal flash drive (which is in the iPad), SSD is 8 - 12, while a flash drive (which is in the iPad) uses 1 - 2. –  klutch2 Feb 19 '11 at 23:46
    
Also, check the iPad tech specs from the Apple web site. 16, 32, and 64 GB flash drive. Not SSD, if it was SSD it would be clearly labeled that way. –  klutch2 Feb 19 '11 at 23:51
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@klutch2 An SSD is "8 - 12", and a flash drive uses "1 - 2"? What does that mean? –  sblair Feb 20 '11 at 1:34
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Flash IS basically the same technology as SSD only the performance of SSD is higher and accordingly the price. @Brian Carlton has a more relevant answer to the question. –  Andris Feb 20 '11 at 17:59
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