Will the usb disk wear out when it is set to read-only

Question

I'm aware that usbs' have a limited read/write cycles. What if, I put a whole linux installation, about 4Gb, on a usb and set the usb to read-only. Then set a ramfs for those apps that needed a writable file-system. Will it affect the life span of the drive or wear it in anyways even without writing?

Answer 1

See the Limitations of Flash Memory.

Read Disturb

The method used to read NAND flash memory can cause nearby cells in the same memory block to change over time (become programmed). This is known as read disturb. The threshold number of reads is generally in the hundreds of thousands of reads between intervening erase operations. If reading continually from one cell, that cell will not fail but rather one of the surrounding cells on a subsequent read.

But:

To avoid the read disturb problem the flash controller will typically count the total number of reads to a block since the last erase. When the count exceeds a target limit, the affected block is copied over to a new block, erased, then released to the block pool. The original block is as good as new after the erase. If the flash controller does not intervene in time, however, a read disturb error will occur with possible data loss if the errors are too numerous to correct with an error-correcting code.

Since the threshold is in the hundreds and thousands of reads, the effect of only reading the flash drive would be minimal; it is more probable that it'd die due to physical harm, rather than because of wearing out.

You should also be aware that there is a lifetime issue with data stored on a flash drive. Data is stored as a series of static charges - over time those charges will dissipate and your data will evaporate, though again, a reasonable expectation for you to run into that problem would be about 10 years.

In conclusion, you can safely assume that your method won't affect the lifespan of your flash drive to the extent that it will be the major cause of your flash drive's eventual death.

More info here and here.