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Do USB pendrives/sticks have random access (i.e. accessing one block will take equal amount of time, regardless of the previous block read) characteristic?

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migrated from unix.stackexchange.com Feb 25 '11 at 16:08

This question came from our site for users of Linux, FreeBSD and other Un*x-like operating systems.

    
Do you want to know if the access is random, or are you just wondering about performance? – skypecakes Mar 1 '11 at 18:54
up vote 3 down vote accepted

No, the access is not truly random since USB flash drives use NAND flash, according to Wikipedia:

With flash memory, only the NOR type is capable of true random access, allowing direct code execution, and is therefore often used instead of ROM; the lower cost NAND type is commonly used for bulk storage in memory cards and solid-state drives.

And:

NAND flash memory forms the core of the removable USB storage devices known as USB flash drives, as well as most memory card formats and solid-state drives available today.

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Reads should all take the same time. Writes are another matter; flash is split into fairly large blocks, and you have to erase all of a block before it can be written to.

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