[maemo-developers] [maemo-developers] Doubts about flash memories and frequent writing

[From: Dave Neuer]

On 1/12/06, Israel Herraiz <israel.herraiz at urjc.es> wrote:
> Hi everybody,
>
> sorry if my question seems too evident.
>
> As far as I know, the Nokia 770 contains a flash memory (128 MB), a RAM
> memory (64 MB) and the MMC card.
>
> All the filesystem is stored in the flash memory, and the MMC is mounted
> in /media/mmc1. Even, you can make swapping with a file in the MMC, as
> appeared some days ago in Planet Maemo.
>
> I am wondering if swapping and every day writing in the internal flash
> could damage these memories. Some people told me that flash memories
> should not be used for frequent disks writing (like swapping or every
> day usage of a computer). Is this relevant? I mean, could I damage the
> flash memory if I use the device very often and I make swap on the MMC
> or internal flash?

Well, AFAICT, the internal flash where the root fs is stored is a
JFFS2 partition which does wear leveling automatically, so for regular
file access patterns I've heard it said that you're unlikely to reach
the 100,000 erase cycles on enough blocks to cause a problem within a
timeframe less than the normal obsolesence of the device, and then
some.

However, I've wondered the same thing about swap; even if one uses
something like JFFS2 and swap to a file (rather than a raw swap
partition), isn't it possible that the writes would be frequent enough
to wear out the eraseblocks too quickly? I don't know even the
beginnings of how swap + I/O interact to get my head around that.

I just bought a 1 GiB mmcMobile card and though I'd love to set up a
swap partition on it, I'd hate to quickly chew up usable space on the
card.

Dave