Re: Overlay ramdisk on filesystem?

[Florian Weimer]

Timothy Miller <miller@xxxxxxxxxxxxxx> writes:

> I have a feeling that this may be a bit too off-topic, but I'm doing
> some Linux and hardware performance tests, and some of the tests will
> put the hardware into an unstable state which could get memory errors
> which could cause filesystem corruption.

In the presence of memory errors, all bets are off anyway.

> I would like to know how I could overlay a RAM disk over a read-only
> filesystem so that all new files and modified files end up in the RAM
> disk, but old files are read from the disk.  This way, when I reboot,
> the disk reverts back.

You might have to tweak the underlying file system, too.  IIRC, ext2
avoids to reallocate freshly deallocated blocks, to prevent
fragmentation.  This will waste a lot of RAM on the long run.

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